Production of ophthalmic devices based on photo-induced step growth polymerization

ABSTRACT

The invention provide a new lens curing method for making hydrogel contact lenses. The new lens curing method is based on actinically-induced step-growth polymerization. The invention also provides hydrogel contact lenses prepared from the method of the invention and fluid compositions for making hydrogel contact lenses based on the new lens curing method. In addition, the invention provide prepolymers capable of undergoing actinically-induced step-growth polymerization to form hydrogel contact lenses.

This application claims the benefits under 35 USC 119(e) of the U.S.Provisional Patent Application No. 60/869,812 filed Dec. 13, 2006 hereinincorporated by reference in its entirety.

The present invention is related to a method for making ophthalmicdevices, in particular hydrogel contact lenses. In particular, thepresent invention is related to a method for cast-molding of hydrogelcontact lenses based on photo-induced step growth polymerization. Inaddition, the present invention is related to actinically crosslinkableprepolymers and compositions useful for making polymeric articles,preferably ophthalmic device, more preferably soft hydrogel contactlenses.

BACKGROUND

A great effort has been made to develop technologies for cast molding ofhydrogel contact lenses with high precision, fidelity andreproducibility and at low cost. One of such manufacturing technologiesis the so-called Lightstream Technology™ (CIBA Vision) involving alens-forming composition being substantially free of monomers andcomprising a substantially purified prepolymer withethylenically-unsaturated groups, reusable molds, and curing under aspatial limitation of actinic radiation (e.g., UV), as described in U.S.Pat. Nos. 5,508,317, 5,583,463, 5,789,464, and 5,849,810. TheLightstream Technology™ for making contact lenses have severaladvantages. First, the curing process is fast, at a time scale ofseconds. Fast curing can ensure design and adaptation of a high speed,continuous and automatic lens production involving on-line lens curing.Second, by using a composition comprising a prepolymer and beingsubstantially free of monomers, subsequent extraction steps (removingunpolymerized monomers from the lenses) required in a traditionalcast-molding manufacturing process are eliminated. Without lensextraction, the production cost can be reduced and the productionefficiency can be further enhanced. Third, reusable quartz/glass moldsor reusable plastic molds, not disposable plastic molds, can be used,because, following the production of a lens, these molds can be cleanedrapidly and effectively of the uncrosslinked prepolymer and otherresidues, using a suitable solvent and can be blown dried with air.Disposable plastic molds inherently have variations in the dimensions,because, during injection-molding of plastic molds, fluctuations in thedimensions of molds can occur as a result of fluctuations in theproduction process (temperatures, pressures, material properties), andalso because the resultant molds may undergo non-uniformly shrinkingafter the injection molding. These dimensional changes in the mold maylead to fluctuations in the parameters of contact lenses to be produced(peak refractive index, diameter, basic curve, central thickness etc.)and to a low fidelity in duplicating complex lens design. By usingreusable molds which are produced in high precision, one can eliminatedimensional variations inherently presented in disposable molds andthereby variation in contact lenses produced therefrom. Lenses producedaccording to the Lightstream Technology™ can have high consistency andhigh fidelity to the original lens design.

However, there are some practical limitations which hinder realizationof all of the great potentials of such technology. For example, alens-forming composition may need to have relatively low viscosity so asto dispense the composition into molds at a high speed. To have arelatively low viscosity, a prepolymer in the composition may have tohave a relatively lower molecular mass. It is believed that themolecular mass of a prepolymer may affect the mechanical strength oflenses made from crosslinking of the prepolymer. Lenses made fromcrosslinking of a prepolymer with a low molecular mass may not have adesired mechanical strength, such as, for example, low tearingresistance. Hydrogel contact lenses having low mechanical strength maynot be suitable for daily- and extended-wear modality.

Accordingly, there is still a need for a lens manufacturing process foreconomically producing durable, highly elastic soft contact lenses withdesired physical properties. There is also need for newactinically-crosslinkable prepolymers suitable for making hydrogelcontact lenses with desired mechanical strength and desired physicalproperties.

SUMMARY OF THE INVENTION

In accomplishing the foregoing, there is provided, in accordance withone aspect of the present invention, a method for producing contactlenses. The method comprises the steps of: (1) obtaining a fluidcomposition, wherein the composition comprises at least one prepolymerhaving multiple first propagating groups each capable of undergoingphoto-induced step-growth polymerization in the presence of or in theabsence of a step-growth-propagating agent having two or more secondpropagating groups each co-reactive with one of the first propagatinggroup in a photo-induced step-growth polymerization to form a hydrogelmaterial; (2) introducing the fluid composition into a cavity formed bya mold, wherein the mold has a first mold half with a first moldingsurface defining the anterior surface of a contact lens and a secondmold half with a second molding surface defining the posterior surfaceof the contact lens, wherein said first and second mold halves areconfigured to receive each other such that a cavity is formed betweensaid first and second molding surfaces; and (3) actinically irradiatingor thermally curing the composition in the mold to crosslink said atleast one prepolymer to form the contact lens.

In another aspect, the invention provides a soft hydrogel contact lens.The contact lens of the invention is obtained by polymerization of afluid composition, wherein the composition comprises at least oneprepolymer having multiple first propagating groups each capable ofundergoing photo-induced step-growth polymerization in the presence ofor in the absence of a step-growth-crosslinking agent having two or moresecond propagating groups each capable of reacting with one of the firstpropagating group in a photo-induced step-growth polymerization,provided that the composition is substantially free of any vinylicmonomer.

In a further aspect, the invention provides a prepolymer suitable formaking soft hydrogel contact lenses. The prepolymer of the inventioncomprises multiple first propagating groups each capable of undergoingphoto-induced step-growth polymerization in the presence of or in theabsence of second propagating groups co-reactive with the firstpropagating group in a photo-induced step-growth polymerization, whereinthe prepolymer is capable of being crosslinked under actinic irradiationto form a hydrogel material in the absence of any vinylic monomer and/orany compound having from two to eight acryloyl or methacryloyl groupsand having a molecular weight of less than 700 Daltons.

In still a further aspect, the invention provides a fluid compositionfor making medical devices, preferably ophthalmic device, morepreferably soft hydrogel contact lenses. The fluid composition of theinvention comprises at least one prepolymer having multiple firstpropagating groups each capable of undergoing photo-induced step-growthpolymerization in the presence of or in the absence of astep-growth-crosslinking agent having two or more second propagatinggroups each co-reactive with one of the first propagating group in aphoto-induced step-growth polymerization, wherein the composition ischaracterized by having a low viscosity and being capable of undergoingphoto-induced step-growth polymerization to crosslink the prepolymer toform a hydrogel material, provided that the composition is substantiallyfree of any vinylic monomer.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Generally, the nomenclatureused herein and the laboratory procedures are well known and commonlyemployed in the art. Conventional methods are used for these procedures,such as those provided in the art and various general references. Wherea term is provided in the singular, the inventors also contemplate theplural of that term. The nomenclature used herein and the laboratoryprocedures described below are those well known and commonly employed inthe art.

An “ophthalmic device”, as used herein, refers to a contact lens (hardor soft), an intraocular lens, a corneal onlay, other ophthalmic devices(e.g., stents, glaucoma shunt, or the like) used on or about the eye orocular vicinity.

“Contact Lens” refers to a structure that can be placed on or within awearer's eye. A contact lens can correct, improve, or alter a user'seyesight, but that need not be the case. A contact lens can be of anyappropriate material known in the art or later developed, and can be asoft lens, a hard lens, or a hybrid lens. A “silicone hydrogel contactlens” refers to a contact lens comprising a silicone hydrogel material.

The “front or anterior surface” of a contact lens, as used herein,refers to the surface of the lens that faces away from the eye duringwear. The anterior surface, which is typically substantially convex, mayalso be referred to as the front curve of the lens.

The “rear or posterior surface” of a contact lens, as used herein,refers to the surface of the lens that faces towards the eye duringwear. The rear surface, which is typically substantially concave, mayalso be referred to as the base curve of the lens.

A “hydrogel” or “hydrogel material” refers to a polymeric material whichcan absorb at least 10 percent by weight of water when it is fullyhydrated.

A “silicone hydrogel” refers to a silicone-containing hydrogel obtainedby copolymerization of a polymerizable composition comprising at leastone silicone-containing monomer or at least one silicone-containingmacromer or at least one crosslinkable silicone-containing prepolymer.

“Hydrophilic,” as used herein, describes a material or portion thereofthat will more readily associate with water than with lipids.

A “monomer” means a low molecular weight compound that can bepolymerized. Low molecular weight typically means average molecularweights less than 700 Daltons.

A “vinylic monomer”, as used herein, refers to a low molecular weightcompound that has an ethylenically unsaturated group and can bepolymerized actinically or thermally. Low molecular weight typicallymeans average molecular weights less than 700 Daltons.

The term “olefinically unsaturated group” or “ethylenticaly unsaturatedgroup” is employed herein in a broad sense and is intended to encompassany groups containing at least one >C═C< group which is directly linkedto a carbonyl group (—CO—), a benzene ring, nitrogen atom, or oxygenatom. Exemplary ethylenically unsaturated groups include withoutlimitation acryloyl, methacryloyl, styrenyl, vinyl carbamate group,vinyl lactam group.

A vinyl lactam has a formula of

which R^(o) is an alkylene divalent radical having from 2 to 8 carbonatoms, R′ is hydrogen, alkyl, aryl, aralkyl or alkaryl, preferablyhydrogen or lower alkyl having up to 7 and, more preferably, up to 4carbon atoms, such as, for example, methyl, ethyl or propyl; aryl havingup to 10 carbon atoms, and also aralkyl or alkaryl having up to 14carbon atoms; and R″ is hydrogen, or lower alkyl having up to 7 and,more preferably, up to 4 carbon atoms, such as, for example, methyl,ethyl or propyl.

As used herein, “actinically” in reference to curing or polymerizing ofa polymerizable composition or material means that the curing (e.g.,crosslinked and/or polymerized) is performed by actinic irradiation,such as, for example, UV irradiation, ionized radiation (e.g. gamma rayor X-ray irradiation), microwave irradiation, and the like. Thermalcuring or actinic curing methods are well-known to a person skilled inthe art.

A “hydrophilic monomer”, as used herein, refers to a monomer which canbe polymerized to form a homopolymer that can absorb at least 10 percentby weight water.

A “hydrophobic monomer”, as used herein, refers to a monomer which canbe polymerized to form a homopolymer that is insoluble in water and canabsorb less than 10 percent by weight water.

A “macromer” refers to a medium and high molecular weight compound orpolymer that contains at least one actinically-crosslinkable group andcan be polymerized and/or crosslinked to form a polymer. Medium and highmolecular weight typically means average molecular weights greater than700 Daltons.

A “prepolymer” refers to a starting polymer which can be cured (e.g.,crosslinked and/or polymerized) actinically or thermally or chemicallyto obtain a crosslinked polymer having a molecular weight much higherthan the starting polymer.

A “silicone-containing prepolymer” refers to a prepolymer which containssilicone and can be crosslinked to obtain a crosslinked polymer having amolecular weight much higher than the starting polymer.

A “polymer” means a material formed by polymerizing/crosslinking one ormore monomers, one or more macromers, one or more prepolymers, ormixtures thereof.

A “photoinitiator” refers to a chemical that initiates radicalcrosslinking/polymerizing reaction by the use of light. Suitablephotoinitiators include, without limitation, benzoin methyl ether,diethoxyacetophenone, a benzoylphosphine oxide, 1-hydroxycyclohexylphenyl ketone, Darocure® types, and Irgacure® types, preferablyDarocure® 1173, and Irgacure® 2959.

A “thermal initiator” refers to a chemical that initiates radicalcrosslinking/polymerizing reaction by the use of heat energy. Examplesof suitable thermal initiators include, but are not limited to,2,2′-azobis (2,4-dimethylpentanenitrile), 2,2′-azobis(2-methylpropanenitrile), 2,2′-azobis (2-methylbutanenitrile), peroxidessuch as benzoyl peroxide, and the like. Preferably, the thermalinitiator is 2,2′-azobis(isobutyronitrile) (AIBN).

An “interpenetrating polymer network (IPN)” as used herein refersbroadly to an intimate network of two or more polymers at least one ofwhich is either synthesized and/or crosslinked in the presence of theother(s). Techniques for preparing IPN are known to one skilled in theart. For a general procedure, see U.S. Pat. Nos. 4,536,554, 4,983,702,5,087,392, and 5,656,210, the contents of which are all incorporatedherein by reference. The polymerization is generally carried out attemperatures ranging from about room temperature to about 145° C.

A “spatial limitation of actinic radiation” refers to an act or processin which energy radiation in the form of rays is directed by means of,for example, a mask or screen or combinations thereof, to impinge, in aspatially restricted manner, onto an area having a well definedperipheral boundary. For example, a spatial limitation of UV radiationcan be achieved by using a mask or screen which has a transparent oropen region (unmasked region) surrounded by a UV impermeable region(masked region), as schematically illustrated in FIGS. 1-9 of U.S. Pat.No. 6,627,124 (herein incorporated by reference in its entirety). Theunmasked region has a well defined peripheral boundary with the unmaskedregion.

“Visibility tinting” in reference to a lens means dying (or coloring) ofa lens to enable the user to easily locate a lens in a clear solutionwithin a lens storage, disinfecting or cleaning container. It is wellknown in the art that a dye and/or a pigment can be used in visibilitytinting a lens.

“Dye” means a substance that is soluble in a solvent and that is used toimpart color. Dyes are typically translucent and absorb but do notscatter light. Any suitable biocompatible dye can be used in the presentinvention.

A “Pigment” means a powdered substance that is suspended in a liquid inwhich it is insoluble. A pigment can be a fluorescent pigment,phosphorescent pigment, pearlescent pigment, or conventional pigment.While any suitable pigment may be employed, it is presently preferredthat the pigment be heat resistant, non-toxic and insoluble in aqueoussolutions.

The term “fluid” as used herein indicates that a material is capable offlowing like a liquid.

“Surface modification”, as used herein, means that an article has beentreated in a surface treatment process (or a surface modificationprocess) prior to or posterior to the formation of the article, in which(1) a coating is applied to the surface of the article, (2) chemicalspecies are adsorbed onto the surface of the article, (3) the chemicalnature (e.g., electrostatic charge) of chemical groups on the surface ofthe article are altered, or (4) the surface properties of the articleare otherwise modified. Exemplary surface treatment processes include,but are not limited to, a surface treatment by energy (e.g., a plasma, astatic electrical charge, irradiation, or other energy source), chemicaltreatments, the grafting of hydrophilic monomers or macromers onto thesurface of an article, mold-transfer coating process disclosed in U.S.Pat. No. 6,719,929 (herein incorporated by reference in its entirety),the incorporation of wetting agents into a lens formulation for makingcontact lenses proposed in U.S. Pat. Nos. 6,367,929, 6,822,016,7,279,507 (herein incorporated by references in their entireties),reinforced mold-transfer coating disclosed in commonly-owned copendingU.S. patent application Ser. No. 11/810,601 (herein incorporated byreference in its entirety), and LbL coating. A preferred class ofsurface treatment processes are plasma processes, in which an ionizedgas is applied to the surface of an article. Plasma gases and processingconditions are described more fully in U.S. Pat. Nos. 4,312,575 and4,632,844, which are incorporated herein by reference. The plasma gas ispreferably a mixture of lower alkanes and nitrogen, oxygen or an inertgas.

“LbL coating”, as used herein, refers to a coating that is notcovalently attached to a contact lens or a mold half and is obtainedthrough a layer-by-layer (“LbL”) deposition of polyionic (or charged)and/or non-charged materials on the lens or mold half. An LbL coatingcan be composed of one or more layers.

As used herein, a “polyionic material” refers to a polymeric materialthat has a plurality of charged groups or ionizable groups, such aspolyelectrolytes, p- and n-type doped conducting polymers. Polyionicmaterials include both polycationic (having positive charges) andpolyanionic (having negative charges) materials.

The term “bilayer” is employed herein in a broad sense and is intendedto encompass: a coating structure formed on a contact lens or a moldhalf by alternatively applying, in no particular order, one layer of afirst polyionic material (or charged material) and subsequently onelayer of a second polyionic material (or charged material) havingcharges opposite of the charges of the first polyionic material (or thecharged material); or a coating structure formed on a contact lens ormold half by alternatively applying, in no particular order, one layerof a first charged polymeric material and one layer of a non-chargedpolymeric material or a second charged polymeric material. It should beunderstood that the layers of the first and second coating materials(described above) may be intertwined with each other in the bilayer.

Formation of an LbL coating on a contact lens or mold half may beaccomplished in a number of ways, for example, as described in U.S. Pat.Nos. 6,451,871, 6,719,929, 6,793,973, 6,811,805, 6,896,926 (hereinincorporated by references in their entireties).

An “innermost layer”, as used herein, refers to the first layer of anLbL coating, which is applied onto the surface of a contact lens or moldhalf.

A “capping layer” or “outmost layer”, as used herein, refers to the lastlayer or the sole layer of an LbL coating which is applied onto acontact lens or mold half.

An “average contact angle” refers to a water contact angle (advancingangle measured by Wilhelmy Plate method), which is obtained by averagingmeasurements of at least 3 individual contact lenses.

An “antimicrobial agent”, as used herein, refers to a chemical that iscapable of decreasing or eliminating or inhibiting the growth ofmicroorganisms such as that term is known in the art.

“Antimicrobial metals” are metals whose ions have an antimicrobialeffect and which are biocompatible. Preferred antimicrobial metalsinclude Ag, Au, Pt, Pd, Ir, Sn, Cu, Sb, Bi and Zn, with Ag being mostpreferred.

“Antimicrobial metal-containing nanoparticles” refer to particles havinga size of less than 1 micrometer and containing at least oneantimicrobial metal present in one or more of its oxidation states.

“Antimicrobial metal nanoparticles” refer to particles which is madeessentially of an antimicrobial metal and have a size of less than 1micrometer. The antimicrobial metal in the antimicrobial metalnanoparticles can be present in one or more of its oxidation states. Forexample, silver-containing nanoparticles can contain silver in one ormore of its oxidation states, such as Ag⁰, Ag¹⁺, and Ag²⁺.

“Stabilized antimicrobial metal nanoparticles” refer to antimicrobialmetal nanoparticles which are stabilized by a stabilizer during theirpreparation. Stabilized antimicrobial metal nano-particles can be eitherpositively charged or negatively charged or neutral, largely dependingon a material (or so-called stabilizer) which is present in a solutionfor preparing the nano-particles and can stabilize the resultantnano-particles. A stabilizer can be any known suitable material.Exemplary stabilizers include, without limitation, positively chargedpolyionic materials, negatively charged polyionic materials, polymers,surfactants, salicylic acid, alcohols and the like.

The “oxygen transmissibility” of a lens, as used herein, is the rate atwhich oxygen will pass through a specific ophthalmic lens. Oxygentransmissibility, Dk/t, is conventionally expressed in units ofbarrers/mm, where t is the average thickness of the material [in unitsof mm] over the area being measured and “barrer/mm” is defined as:[(cm³oxygen)/(cm²)(sec)(mm²Hg)]×10⁻⁹

The intrinsic “oxygen permeability”, Dk, of a lens material does notdepend on lens thickness. Intrinsic oxygen permeability is the rate atwhich oxygen will pass through a material. Oxygen permeability isconventionally expressed in units of barrers, where “barrer” is definedas:[(cm³oxygen)(mm)/(cm²)(sec)(mm²Hg)]×10⁻¹⁰These are the units commonly used in the art. Thus, in order to beconsistent with the use in the art, the unit “barrer” will have themeanings as defined above. For example, a lens having a Dk of 90 barrers(“oxygen permeability barrers”) and a thickness of 90 microns (0.090 mm)would have a Dk/t of 100 barrers/mm

$\left( {\frac{90 \times 10^{- 10}}{0.09} = {100 \times 10^{- 9}}} \right)$(oxygen transmissibility barrers/mm). In accordance with the invention,a high oxygen permeability in reference to a material or a contact lenscharacterized by apparent oxygen permeability of at least 40 barrers orlarger measured with a sample (film or lens) of 100 microns in thicknessaccording to a coulometric method described in Examples.

The “ion permeability” through a lens correlates with both the IonofluxDiffusion Coefficient and the Ionoton Ion Permeability Coefficient.

The Ionoflux Diffusion Coefficient, D, is determined by applying Fick'slaw as follows:D=−n′/(A×dc/dx)where n′=rate of ion transport [mol/min]

A=area of lens exposed [mm²]

D=Ionoflux Diffusion Coefficient [mm²/min]

dc=concentration difference [mol/L]

dx=thickness of lens [mm]

The Ionoton Ion Permeability Coefficient, P, is then determined inaccordance with the following equation:ln(1−2C(t)/C(0))=−2APt/Vdwhere C(t)=concentration of sodium ions at time t in the receiving cell

C(0)=initial concentration of sodium ions in donor cell

A=membrane area, i.e., lens area exposed to cells

V=volume of cell compartment (3.0 ml)

d=average lens thickness in the area exposed

P=permeability coefficient

An Ionoflux Diffusion Coefficient, D, of greater than about 1.5×10⁻⁶mm²/min is preferred, while greater than about 2.6×10⁻⁶ mm²/min is morepreferred and greater than about 6.4×10⁻⁶ mm²/min is most preferred.

It is known that on-eye movement of the lens is required to ensure goodtear exchange, and ultimately, to ensure good corneal health. Ionpermeability is one of the predictors of on-eye movement, because thepermeability of ions is believed to be directly proportional to thepermeability of water.

In general, the invention is directed to a method for economicallyproducing durable, highly elastic hydrogel contact lenses with desiredmechanical and physical properties. The invention is partly based on thediscovery that a new lens curing method based on step-growthpolymerization, different from current curing method used in contactlenses industry, can be advantageously and directly used in cast-moldingof hydrogel contact lenses with desirable mechanical and physicalproperties. Such new lens curing mechanism can overcome shortcomings ofconventional lens-curing mechanism based on free radical chain-growthpolymerization. For example, although free radical chain-growthpolymerization is rapid, molecular mass between crosslinks may be quitelow and the resultant polymer may have undesirably high E-modulus, lowtearing resistance, and/or other non-optimal mechanical or physicalproperties. It is believed that molecular mass between crosslinks isgenerally dictated by the molecular mass of starting macromer orprepolymer. As such, in order to enhance the mechanical properties(e.g., tear resistance) of contact lenses, prepolymers with highmolecular mass have to be used in compositions for making contact lensesbased on free radical chain-growth polymerization. But, prepolymers withhigh molecular mass will inevitably increase greatly the viscosity ofthe polymerizable composition and thereby the processing ability (e.g.,dosing in molds) of the polymerizable composition is greatly hindered.In addition, resultant polymers form at near-zero monomer conversionbecause of the chain-growth nature of the polymerization, leading veryhigh viscosity at low conversion and inducing stress in the formednetwork of a hydrogel.

However, it is discovered here that lens curing method based onphoto-induced step growth polymerization can have advantages overtraditional lens curing method (i.e., free radical chain-growthpolymerization). First, the photo-induced step-growth polymerization canbe rapid, e.g., in a timescale of seconds. Such lens curing can beeasily implemented in the Lightstream Technology™. Second, it isbelieved that under step-growth polymerization, each chain end reactswith only one other chain end, leading to buildup of molecular massbetween crosslinks. With high molecular mass between crosslinks, themechanical strength, such as, e.g., tear resistance or the like, can beexpectedly enhanced. Third, it is believed that because resultantpolymers form at high conversion of monomers, the viscosity of thereaction system remains low until high conversion and polymerizationwould induce lower stress in the network of a hydrogel. Prepolymershaving relatively lower molecular mass can be used to produce contactlenses with desirable mechanical properties. The viscosity of apolymerizable composition with such prepolymers can be relatively low.Fourth, step-growth polymerization can be used in combination with freeradical chain-growth polymerization to provide a polymerizablecomposition tailorable for a wide range of mechanical and physicalproperties.

The present invention, in one aspect, provides a method for producingcontact lenses. The method of the invention comprises the steps of: (1)obtaining a fluid composition, wherein the composition comprises atleast one prepolymer having multiple first propagating groups eachcapable of undergoing photo-induced step-growth polymerization in thepresence of or in the absence of a step-growth-crosslinking agent havingtwo or more second propagating groups each co-reactive with one of thefirst propagating group in a photo-induced step-growth polymerization;(2) introducing the fluid composition into a cavity formed by a mold,wherein the mold has a first mold half with a first molding surfacedefining the anterior surface of a contact lens and a second mold halfwith a second molding surface defining the posterior surface of thecontact lens, wherein said first and second mold halves are configuredto receive each other such that a cavity is formed between said firstand second molding surfaces; and (3) actinically irradiating thecomposition in the mold to crosslink said at least one prepolymer toform the contact lens.

In accordance with the invention, a prepolymer of the invention isobtained from a copolymer with pendant or terminal functional group byfunctionalizing the copolymer to include multiple propagating groupseach capable of undergoing photo-induced step-growth polymerization inthe presence of or in the absence of a step-growth-crosslinking agenthaving two or more second propagating groups each co-reactive with oneof the first propagating group in a photo-induced step-growthpolymerization.

As used herein, the term “functionalize” in reference to a copolymer isintended to describe that propagating groups have been covalentlyattached to a copolymer through the pendant or terminal functionalgroups of the copolymer according to a chemical process.

As used herein, the term “multiple” refers to three or more.

In accordance with the invention, any propagating groups can be used inthe invention so long as the propagating groups are involved in astep-growth polymerization under actinic irradiation (preferably UVirradiation).

One preferred step-growth polymerization is thiol-ene step-growthradical polymerization, which proceeds via propagation of thiyl radical(—S*) through the vinyl group. Rather than being followed by additionalpropagation, this propagation step is continually followed by chaintransfer of the carbon radical (—CH—), thus formed, to the thiol group,regenerating a thiyl radical (Scheme I).

As shown in Scheme I, a pair of propagating groups, a thiol and a vinylgroup, are required in photoinduced thiol-ene polymerization.

Another preferred step-growth polymerization is 2+2 cycloadditions, suchas, for example, photoinduced dimerization of 2-nitrocinnamic acid(scheme II), and the photoinduced dialkyl maleiimide cycloaddition(Scheme III). As shown in schemes II and III, one propagating group isrequired in 2+2 cycladditions.

In a preferred embodiment, a prepolymer comprises multiple propagatinggroups selected from the group consisting of thiol groups,ene-containing groups, cinnamic acid moities, dialkylmaleimide groups,and combinations thereof.

In accordance with the invention, an ene-containing group is intended todescribe that a mono-valent or divalent radical contains a carbon-carbondouble which is not directly linked to a carbonyl group (—CO—), abenzene ring, nitrogen atom, or oxygen atom. Preferably, theene-containing group is defined by any one of formula (I)-(III)

in which R₁ is hydrogen, or C₁-C₁₀ alkyl; R₂ and R₃ independent of eachother are hydrogen, C₁-C₁₀ alkene divalent radical, C₁-C₁₀ alkyl, or—(R₁₈)_(a)—(X₁)_(b)—R₁₉ in which R₁₈ is C₁-C₁₀ alkene divalent radical,X₁ is an ether linkage (—O—), a urethane linkage (—N), a urea linkage,an ester linkage, an amid linkage, or carbonyl, R₁₉ is hydrogen, asingle bond, amino group, carboxylic group, hydroxyl group, carbonylgroup, C₁-C₁₂ aminoalkyl group, C₁-C₁₈ alkylaminoalkyl group, C₁-C₁₈carboxyalkyl group, C₁-C₁₈ hydroxyalkyl group, C₁-C₁₈ alkylalkoxy group,C₁-C₁₂ aminoalkoxy group, C₁-C₁₈ alkylaminoalkoxy group, C₁-C₁₈carboxyalkoxy group, or C₁-C₁₈ hydroxyalkoxy group, a and b independentof each other is zero or 1, provided that only one of R₂ and R₃ is adivalent radical; R₄-R₁₉, independent of each other, are hydrogen,C₁-C₁₀ alkene divalent radical, C₁-C₁₀ alkyl, or—(R₁₈)_(a)—(X₁)_(b)—R₁₉, optionally R₄ and R₉ are linked through analkene divalent radical to form a cyclic ring, provided that at leastone of R₄-R₉ are divalent radicals; n and m independent of each otherare integer number from 0 to 9, provided that the sum of n and m is aninteger number from 2 to 9; R₁₀-R₁₇, independent of each other, arehydrogen, C₁-C₁₀ alkene divalent radical, C₁-C₁₀ alkyl, or—(R₁₈)_(a)—(X₁)_(b)—R₁₉, p is an integer number from 1 to 3, providedthat only one or two of R₁₀-R₁₇ are divalent radicals.

In accordance with the invention, a cinnamic acid moiety is intended todescribe that a mono-valent or divalent radical which is defined byformula (IV)

in which R₂₀-R₂₅, independent of each other, are hydrogen, C₁-C₁₀ alkenedivalent radical, C₁-C₁₀ alkyl, or —(R₁₈)_(a)—(X₁)_(b)—R₁₉, providedthat R₂₁ or R₂₅ is —NO₂, provided that only one or two of R₂₀-R₂₅ aredivalent radicals.

In accordance with the invention, a dialkylmaleimide group is intendedto describe that a mono-valent radical which is defined by formula (V)

in which R₂₆ and R₂₇, independent of each other, are hydrogen or C₁-C₁₀alkyl and R₂₈ is a C₁-C₁₀ alkene divalent radical.

Where the prepolymer comprises multiple ene-containing groups, thesegroups undergo thiol-ene step-growth radical polymerization only in thepresence of thiols groups which can be provided by astep-growth-crosslinking agent having two or more thiol groups.Similarly, where the prepolymer comprises multiple thiol groups, thesegroups undergo thiol-ene step-growth radical polymerization only in thepresence of ene-containing groups which can be provided by astep-growth-crosslinking agent having two or more ene-containing groups.

Where the prepolymer comprises multiple cinnamic acid moieties ordialkylamleimide groups, these groups can undergo photoinduced 2+2cycloaddition polymerization in the absence of other propagating groupsprovided by a step-growth-crosslinking agent.

A prepolymer of the invention is capable of forming a hydrogel material(non-silicone hydrogel or silicone hydrogel), preferably in the absenceof any hydrophilic vinylic monomer, and can be obtained by covalentlyattaching thiol groups, ene-containing groups, cinnamic acid moieties,or dialkylamleimide groups to the pendant or terminal functional groupsof a copolymer according to any known covalently coupling method. It iswell known in the art that a pair of matching crosslinkable groups canform a covalent bond or linkage under known reaction conditions, suchas, oxidation-reduction conditions, dehydration condensation conditions,addition conditions, substitution (or displacement) conditions,Diels-Alder reaction conditions, cationic crosslinking conditions, andepoxy hardening conditions. For example, an amino group is covalentlybondable with aldehyde (Schiff base which is formed from aldehyde groupand amino group may further be reduced); an amino group is covalentlybondable with an acid chloride, an anhydride or an isocyanate; anhydroxyl is covalently bondable with an acid chloride, an isocyanate orepoxy; or the likes.

Exemplary covalent bonds or linkage, which are formed between pairs ofcrosslinkable groups, include without limitation, ester, ether, acetal,ketal, vinyl ether, carbamate, urea, urethane, amine, amide, enamine,imine, oxime, amidine, iminoester, carbonate, orthoester, phosphonate,phosphinate, sulfonate, sulfinate, sulfide, sulfate, disulfide,sulfinamide, sulfonamide, thioester, aryl, silane, siloxane,heterocycles, thiocarbonate, thiocarbamate, and phosphonamide.

Exemplary crosslinkable groups include hydroxyl group, amine group,amide group, anhydride group, sulfhydryl group, —COOR (R and R′ arehydrogen or C₁ to C₈ alkyl groups), halide (chloride, bromide, iodide),acyl chloride, isothiocyanate, isocyanate, monochlorotriazine,dichlorotriazine, mono- or di-halogen substituted pyridine, mono- ordi-halogen substituted diazine, phosphoramidite, maleimide, aziridine,sulfonyl halide, hydroxysuccinimide ester, hydroxysulfosuccinimideester, imido ester, hydrazine, axidonitrophenyl group, azide,3-(2-pyridyl dithio)proprionamide, glyoxal, aldehyde, epoxy.

As an illustrative example, a prepolymer of the invention can beobtained by reacting a compound including a first crosslinkable groupand a thiol group, a ene-containing group, a cinnamic acid moiety, or adialkylamleimide group with a copolymer including multiple secondcrosslinkable groups, wherein the first crosslinkable group reacts withone second crosslinkable group to form a covalent bond or linkage asdescribed above.

It is understood that coupling agents may be used. Coupling agentsuseful for coupling include, without limitation, N.N′-carbonyldiimidazole, carbodiimides such as1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (“EDC”), dicyclohexylcarbodiimide, 1-cylcohexyl-3-(2-morpholinoethyl)carbodiimide,diisopropyl carbodiimide, or mixtures thereof. The carbodiimides alsomay be used with N-hydroxysuccinimide or N-hydroxysulfosuccinimide toform esters that can react with amines to form amides.

A copolymer with pendant or terminal groups should be soluble in water,an organic solvent or a mixture of water and at least one organicsolvent. Any copolymers including pendant or terminal functional groupscan be used in the invention. Examples of preferred copolymers include:without limitation, copolymers of vinyl alcohol with one or more vinylicmonomers in the presence or absence of a crosslinking agent; copolymersof C₃-C₈ aminoalkylacrylate with one or more vinylic monomers in thepresence or absence of a crosslinking agent; copolymers of C₃-C₈hydroxyalkylacrylate with one or more vinylic monomers in the presenceor absence of a crosslinking agent; copolymers of C₄-C₈aminoalkylmethacrylate with one or more vinylic monomers in the presenceor absence of a crosslinking agent; copolymers of C₄-C₈hydroxyalkylmethacrylate with one or more vinylic monomers in thepresence or absence of a crosslinking agent; copolymers of C₃-C₈alkylacrylic acid with one or more vinylic monomers in the presence orabsence of a crosslinking agent; copolymers of C₄-C₈ alkylmethacrylicwith one or more vinylic monomers in the presence or absence of acrosslinking agent; copolymers of an epoxy-containing acrylate monomerwith one or more vinylic monomers in the presence or absence of acrosslinking agent; copolymers of an epoxy-containing methacrylatemonomer with one or more vinylic monomers in the presence or absence ofa crosslinking agent; an amine- or isocyanate-capped polyurea obtainedby copolymerization of a mixture comprising (a) at least onepoly(oxyalkylene)diamine, (b) optionally at least one organic di- orpoly-amine, (c) optionally at least one diisocyanate, and (d) at leastone polyisocyanate; a hydroxy- or isocyanate-capped polyurethaneobtained by copolymerization of a mixture comprising (a) at least onepoly(oxyalkylene)diol, (b) optionally at least one organic compound withdi- or poly-hydroxy group, (c) optionally at least one diisocyanate, and(d) at least one polyisocyanate; siloxane-containing copolymers obtainedby copolymerizing a mixture containing at least one siloxane-containingvinylic monomer, at least one siloxane-containing macromer, at least onesilicone-containing prepolymer, or mixture thereof; and a copolymer of apoly(di-C₁₋₁₂ alkylsiloxane) with one or more coreactive monomers.

Alternatively, an ene-containing prepolymer of the invention can beprepared by copolymerizing a polymerizable composition including atleast one monomer having one ene-group of formula (I, (II), or (III) andone ethylenically unsaturate group. The ene-group can survive (i.e.,hardly participate), whereas the ethylenically unsaturated group willparticipate (i.e., be consumed), in a free radical polymerization in theabsence of a thiol-containing compound. Examples of ene-containingacrylate or methacrylate include, without limitation.

In a preferred embodiment, a step-growth-crosslinking agent comprisestwo or more thiol groups or ene-containing groups which are co-reactivewith the first propagating groups of the prepolymer in a photo-inducedstep-growth polymerization. More preferably, a step-growth-crosslinkingagent is a prepolymer comprising multiple thiol groups or ene-containinggroups.

Preferably, the prepolymers used in the invention are previouslypurified in a manner known per se, for example by precipitation withorganic solvents, such as acetone, filtration and washing, extraction ina suitable solvent, dialysis or ultrafiltration, ultrafiltration beingespecially preferred. By means of that purification process theprepolymers can be obtained in extremely pure form, for example in theform of concentrated solutions that are free, or at least substantiallyfree, from reaction products, such as salts, and from startingmaterials, such as, for example, non-polymeric constituents. Thepreferred purification process for the prepolymers used in the processaccording to the invention, ultrafiltration, can be carried out in amanner known per se. It is possible for the ultrafiltration to becarried out repeatedly, for example from two to ten times.Alternatively, the ultrafiltration can be carried out continuously untilthe selected degree of purity is attained. The selected degree of puritycan in principle be as high as desired. A suitable measure for thedegree of purity is, for example, the concentration of dissolved saltsobtained as by-products, which can be determined simply in known manner.Thus, after polymerization, the device will not require subsequentpurification such as, for example, costly and complicated extraction ofunpolymerized matrix-forming material. Furthermore, crosslinking of theprepolymer can take place absent a solvent or in aqueous solution sothat a subsequent solvent exchange or the hydration step is notnecessary.

In a preferred embodiment, the fluid composition comprises a prepolymerhaving multiple ene-containing groups defined by one of formula (I) to(III) and a step-growth-crosslinking agent having two or more thiolgroups. The ene-containing groups are preferably defined by formula(II), more preferably defined by formula (III). Preferably, thestep-growth-crosslinking agent is a prepolymer having multiple thiolgroups. All the prepolymers in this embodiment are purifiedsubstantially before adding into the fluid composition.

In another preferred embodiment, the fluid composition comprises aprepolymer having multiple ene-containing groups defined by one offormula (I) to (III), a step-growth-crosslinking agent having two ormore thiol groups, and a prepolymer having multiple acryloyl

or methacryloyl

groups. The ene-containing groups are preferably defined by formula(II), more preferably defined by formula (III). Preferably, thestep-growth-crosslinking agent is a prepolymer having multiple thiolgroups. All the prepolymers in this embodiment are purifiedsubstantially before adding into the fluid composition.

By having both ene-containing groups and acryloyl (or methacryloyl)groups in the fluid composition, one can have two types ofpolymerization during the curing process: thiol-ene step-growth radicalpolymerization and free radical chain-growth polymerization. Byadjusting these two types of polymerization, one may be able to tail afluid composition for making contact lenses with a wide range ofmechanical and physical properties.

Examples of prepolymers with multiple acryloyl or methacryloyl groupsinclude, but are not limited to, a water-soluble crosslinkablepoly(vinyl alcohol) prepolymer described in U.S. Pat. Nos. 5,583,163 and6,303,687 (incorporated by reference in their entireties); awater-soluble vinyl group-terminated polyurethane prepolymer describedin U.S. Patent Application Publication No. 2004/0082680 (hereinincorporated by reference in its entirety); derivatives of a polyvinylalcohol, polyethyleneimine or polyvinylamine, which are disclosed inU.S. Pat. No. 5,849,841 (incorporated by reference in its entirety); awater-soluble crosslinkable polyurea prepolymer described in U.S. Pat.No. 6,479,587 and in U.S. Published Application No. 2005/0113549 (hereinincorporated by reference in their entireties); crosslinkablepolyacrylamide; crosslinkable statistical copolymers of vinyl lactam,MMA and a comonomer, which are disclosed in EP 655,470 and U.S. Pat. No.5,712,356 (herein incorporated by reference in their entireties);crosslinkable copolymers of vinyl lactam, vinyl acetate and vinylalcohol, which are disclosed in EP 712,867 and U.S. Pat. No. 5,665,840(herein incorporated by reference in their entireties);polyether-polyester copolymers with crosslinkable side chains which aredisclosed in EP 932,635 and U.S. Pat. No. 6,492,478 (herein incorporatedby reference in their entireties); branched polyalkylene glycol-urethaneprepolymers disclosed in EP 958,315 and U.S. Pat. No. 6,165,408 (hereinincorporated by reference in their entireties); polyalkyleneglycol-tetra(meth)acrylate prepolymers disclosed in EP 961,941 and U.S.Pat. No. 6,221,303 (herein incorporated by reference in theirentireties); crosslinkable polyallylamine gluconolactone prepolymersdisclosed in International Application No. WO 2000/31150 and U.S. Pat.No. 6,472,489 (herein incorporated by reference in their entireties);silicone-containing prepolymers are those described in U.S. PublishedApplication No. 2001-0037001 A1, U.S. Pat. No. 6,039,913, U.S. patentapplication No. 60/830,288 (herein incorporated by reference in theirentireties).

In another preferred embodiment, the fluid composition comprises asilicone-containing prepolymer having multiple ene-containing groupsdefined by one of formula (I) to (III) and a step-growth-crosslinkingagent having two or more thiol groups. The ene-containing groups arepreferably defined by formula (II), more preferably defined by formula(III). Preferably, the step-growth-crosslinking agent is a prepolymerhaving multiple thiol groups. The thiol-containing prepolymer can besilicone free prepolymer or silicone-containing prepolymer. All theprepolymers in this embodiment preferably are purified substantiallybefore being added into the fluid composition.

In another preferred embodiment, the fluid composition comprises asilicone-containing prepolymer having multiple ene-containing groupsdefined by one of formula (I) to (III), a step-growth-crosslinking agenthaving two or more thiol groups, and a prepolymer having multipleacryloyl

or methacryloyl

groups. The ene-containing groups are preferably defined by formula(II), more preferably defined by formula (III). Preferably, thestep-growth-crosslinking agent is a prepolymer having multiple thiolgroups. The thiol-containing prepolymer can be silicone free prepolymeror silicone-containing prepolymer. All the prepolymers in thisembodiment preferably are purified substantially before being added intothe fluid composition.

The fluid composition can optionally comprises one or more vinylicmonomer and/or one or more crosslinking agents (i.e., compounds with twoor more ethylenically unsaturated groups and with molecular weight lessthan 700 Daltons). However, the amount of those components should be lowsuch that the final ophthalmic device does not contain unacceptablelevels of unpolymerized monomers and/or crosslinking agents. Thepresence of unacceptable levels of unpolymerized monomers and/orcrosslinking agents will require extraction to remove them, whichrequires additional steps that are costly and inefficient. Butpreferably, the fluid composition is substantially free of vinylicmonomer and crosslinking agent (i.e., preferably about 2% or less, morepreferably about 1% or less, even more preferably about 0.5% or less byweight).

The composition can be a solution, a solvent-free liquid, or a melt.Preferably, a fluid composition is a solution of at least one prepolymerin water, or an organic solvent, or a mixture of water and one or moreorganic solvents.

A solution of at least one prepolymer can be prepared by dissolving theprepolymer and other components in any suitable solvent known to aperson skilled in the art. Examples of suitable solvents are, withoutlimitation, water, alcohols (e.g., methanol, ethanol, propanol, oralkanols having 4 to 15 carbons), carboxylic acid amides (e.g.,dimethylformamide), dipolar aprotic solvents (e.g., dimethyl sulfoxideor methyl ethyl ketone), ketones (e.g., acetone or cyclohexanone),hydrocarbons (e.g., toluene), ethers, tetrahydrofuran (THF),dimethoxyethane, dioxane, diethylenglycolmonoethylether,diethylenglycolmonomethylether, diethylenglycoldimethylether,diethylenglycoldiethylether, halogenated hydrocarbons (e.g.,trichloroethane), and mixtures thereof.

It must be understood that a fluid composition can also comprise variouscomponents, such as, for example, polymerization initiators (e.g.,photoinitiator or thermal initiator), a visibility tinting agent (e.g.,dyes, pigments, or mixtures thereof), UV-blocking agent,photosensitizers, inhibitors, antimicrobial agents (e.g., preferablysilver nanoparticles or stabilized silver nanoparticles), bioactiveagent, lubricants, fillers, and the like, as known to a person skilledin the art.

Initiators, for example, selected from materials well known for such usein the polymerization art, may be included in the polymerizable fluidcomposition in order to promote, and/or increase the rate of, thepolymerization reaction. An initiator is a chemical agent capable ofinitiating polymerization reactions. The initiator can be aphotoinitiator or a thermal initiator.

A photoinitiator can initiate free radical polymerization and/orcrosslinking by the use of light. Suitable photoinitiators are benzoinmethyl ether, diethoxyacetophenone, a benzoylphosphine oxide,1-hydroxycyclohexyl phenyl ketone and Darocur and Irgacur types,preferably Darocur 1173® and Darocur 2959®. Examples of benzoylphosphineinitiators include 2,4,6-trimethylbenzoyldiphenylophosphine oxide;bis-(2,6-dichlorobenzoyl)-4-N-propylphenylphosphine oxide; andbis-(2,6-dichlorobenzoyl)-4-N-butylphenylphosphine oxide. Reactivephotoinitiators which can be incorporated, for example, into a macromeror can be used as a special monomer are also suitable. Examples ofreactive photoinitiators are those disclosed in EP 632 329, hereinincorporated by reference in its entirety. The polymerization can thenbe triggered off by actinic radiation, for example light, in particularUV light of a suitable wavelength. The spectral requirements can becontrolled accordingly, if appropriate, by addition of suitablephotosensitizers

Examples of suitable thermal initiators include, but are not limited to,2,2′-azobis (2,4-dimethylpentanenitrile), 2,2′-azobis(2-methylpropanenitrile), 2,2′-azobis (2-methylbutanenitrile), peroxidessuch as benzoyl peroxide, and the like. Preferably, the thermalinitiator is azobisisobutyronite (AIBN).

Examples of preferred pigments include any colorant permitted in medicaldevices and approved by the FDA, such as D&C Blue No. 6, D&C Green No.6, D&C Violet No. 2, carbazole violet, certain copper complexes, certainchromium oxides, various iron oxides, phthalocyanine green,phthalocyanine blue, titanium dioxides, etc. See Marmiom DM Handbook ofU.S. Colorants for a list of colorants that may be used with the presentinvention. A more preferred embodiment of a pigment include (C.I. is thecolor index no.), without limitation, for a blue color, phthalocyanineblue (pigment blue 15:3, C.I. 74160), cobalt blue (pigment blue 36, C.I.77343), Toner cyan BG (Clariant), Permajet blue B2G (Clariant); for agreen color, phthalocyanine green (Pigment green 7, C.I. 74260) andchromium sesquioxide; for yellow, red, brown and black colors, variousiron oxides; PR122, PY154, for violet, carbazole violet; for black,Monolith black C-K (CIBA Specialty Chemicals).

The bioactive agent incorporated in the polymeric matrix is any compoundthat can prevent a malady in the eye or reduce the symptoms of an eyemalady. The bioactive agent can be a drug, an amino acid (e.g., taurine,glycine, etc.), a polypeptide, a protein, a nucleic acid, or anycombination thereof. Examples of drugs useful herein include, but arenot limited to, rebamipide, ketotifen, olaptidine, cromoglycolate,cyclosporine, nedocromil, levocabastine, lodoxamide, ketotifen, or thepharmaceutically acceptable salt or ester thereof. Other examples ofbioactive agents include 2-pyrrolidone-5-carboxylic acid (PCA), alphahydroxyl acids (e.g., glycolic, lactic, malic, tartaric, mandelic andcitric acids and salts thereof, etc.), linoleic and gamma linoleicacids, and vitamins (e.g., B5, A, B6, etc.).

Examples of lubricants include without limitation mucin-like materialsand hydrophilic polymers. Exemplary mucin-like materials include withoutlimitation polyglycolic acid, polylactides, collagen, hyaluronic acid,and gelatin.

Exemplary hydrophilic polymers include, but are not limited to,polyvinyl alcohols (PVAs), polyamides, polyimides, polylactone, ahomopolymer of a vinyl lactam, a copolymer of at least one vinyl lactamin the presence or in the absence of one or more hydrophilic vinyliccomonomers, a homopolymer of acrylamide or methacrylamide, a copolymerof acrylamide or methacrylamide with one or more hydrophilic vinylicmonomers, polyethylene oxide (i.e., polyethylene glycol (PEG)), apolyoxyethylene derivative, poly-N—N-dimethylacrylamide, polyacrylicacid, poly 2 ethyl oxazoline, heparin polysaccharides, polysaccharides,and mixtures thereof.

Examples of N-vinyl lactams include N-vinyl-2-pyrrolidone,N-vinyl-2-piperidone, N-vinyl-2-caprolactam,N-vinyl-3-methyl-2-pyrrolidone, N-vinyl-3-methyl-2-piperidone,N-vinyl-3-methyl-2-caprolactam, N-vinyl-4-methyl-2-pyrrolidone,N-vinyl-4-methyl-2-caprolactam, N-vinyl-5-methyl-2-pyrrolidone,N-vinyl-5-methyl-2-piperidone, N-vinyl-5,5-dimethyl-2-pyrrolidone,N-vinyl-3,3,5-trimethyl-2-pyrrolidone,N-vinyl-5-methyl-5-ethyl-2-pyrrolidone,N-vinyl-3,4,5-trimethyl-3-ethyl-2-pyrrolidone,N-vinyl-6-methyl-2-piperidone, N-vinyl-6-ethyl-2-piperidone,N-vinyl-3,5-dimethyl-2-piperidone, N-vinyl-4,4-dimethyl-2-piperidone,N-vinyl-7-methyl-2 -caprolactam, N-vinyl-7-ethyl-2-caprolactam,N-vinyl-3,5-dimethyl-2-caprolactam, N-vinyl-4,6-dimethyl-2-caprolactam,and N-vinyl-3,5,7-trimethyl-2-caprolactam.

The number-average molecular weight M_(n) of the hydrophilic polymer is,for example, greater than 10,000, or greater than 20,000, than that ofthe matrix forming material. For example, when the matrix formingmaterial is a water-soluble prepolymer having an average molecularweight M_(n) of from 12,000 to 25,000, the average molecular weightM_(n) of the hydrophilic polymer is, for example, from 25,000 to 100000,from 30,000 to 75,000, or from 35,000 to 70,000.

A suitable polyoxyethylene derivative is, for example, n-alkylphenylpolyoxyethylene ether, n-alkyl polyoxy-ethylene ether (e.g., TRITON®),polyglycol ether surfactant (TERGITOL®), polyoxyethylenesorbitan (e.g.,TWEEN®), polyoxyethylated glycol monoether (e.g., BRIJ®,polyoxylethylene 9 lauryl ether, polyoxylethylene 10 ether,polyoxylethylene 10 tridecyl ether), or a block copolymer of ethyleneoxide and propylene oxide.

Examples of block copolymers of ethylene oxide and propylene oxideinclude without limitation poloxamers and poloxamines, which areavailable, for example, under the tradename PLURONIC®, PLURONIC-R®,TETRONIC®, TETRONIC-R® or PLURADOT®. Poloxamers are triblock copolymerswith the structure PEO-PPO-PEO (where “PEO” is poly(ethylene oxide) and“PPO” is poly(propylene oxide).

A considerable number of poloxamers is known, differing merely in themolecular weight and in the PEO/PPO ratio; Examples of poloxamersinclude 101, 105, 108, 122, 123, 124, 181, 182, 183, 184, 185, 188, 212,215, 217, 231, 234, 235, 237, 238, 282, 284, 288, 331, 333, 334, 335,338, 401, 402, 403 and 407. The order of polyoxyethylene andpolyoxypropylene blocks can be reversed creating block copolymers withthe structure PPO-PEO-PPO, which are known as PLURONIC-R® polymers.

Poloxamines are polymers with the structure(PEO-PPO)₂—N—(CH₂)₂—N—(PPO-PEO)₂ that are available with differentmolecular weights and PEO/PPO ratios. Again, the order ofpolyoxyethylene and polyoxypropylene blocks can be reversed creatingblock copolymers with the structure (PPO-PEO)₂—N—(CH₂)₂—N-(PEO-PPO)₂,which are known as TETRONIC-R® polymers.

Polyoxypropylene-polyoxyethylene block copolymers can also be designedwith hydrophilic blocks comprising a random mix of ethylene oxide andpropylene oxide repeating units. To maintain the hydrophilic characterof the block, ethylene oxide will predominate. Similarly, thehydrophobic block can be a mixture of ethylene oxide and propylene oxiderepeating units. Such block copolymers are available under the tradenamePLURADOT®.

In accordance with the invention, the fluid composition can beintroduced (dispensed) into a cavity formed by a mold according to anyknown methods.

Lens molds for making contact lenses are well known to a person skilledin the art and, for example, are employed in cast molding or spincasting. For example, a mold (for cast molding) generally comprises atleast two mold sections (or portions) or mold halves, i.e. first andsecond mold halves. The first mold half defines a first molding (oroptical) surface and the second mold half defines a second molding (oroptical) surface. The first and second mold halves are configured toreceive each other such that a lens forming cavity is formed between thefirst molding surface and the second molding surface. The moldingsurface of a mold half is the cavity-forming surface of the mold and indirect contact with lens-forming material.

Methods of manufacturing mold sections for cast-molding a contact lensare generally well known to those of ordinary skill in the art. Theprocess of the present invention is not limited to any particular methodof forming a mold. In fact, any method of forming a mold can be used inthe present invention. The first and second mold halves can be formedthrough various techniques, such as injection molding or lathing.Examples of suitable processes for forming the mold halves are disclosedin U.S. Pat. Nos. 4,444,711 to Schad; 4,460,534 to Boehm et al.;5,843,346 to Morrill; and 5,894,002 to Boneberger et al., which are alsoincorporated herein by reference.

Virtually all materials known in the art for making molds can be used tomake molds for preparing ocular lenses. For example, polymericmaterials, such as polyethylene, polypropylene, polystyrene, PMMA,cyclic olefin copolymers (e.g., Topas® COC from Ticona GmbH ofFrankfurt, Germany and Summit, N.J.; Zeonex® and Zeonor® from ZeonChemicals LP, Louisville, Ky.), or the like can be used. Other materialsthat allow UV light transmission could be used, such as quartz glass andsapphire.

In a preferred embodiment, when the polymerizable components in thefluid composition is composed essentially of prepolymers, reusable moldscan be used. Examples of reusable molds made of quartz or glass arethose disclosed in U.S. Pat. No. 6,627,124, which is incorporated byreference in their entireties. In this aspect, the fluid composition ispoured into a mold consisting of two mold halves, the two mold halvesnot touching each other but having a thin gap of annular design arrangedbetween them. The gap is connected to the mold cavity, so that excessprepolymer composition can flow into the gap. Instead of polypropylenemolds that can be used only once, it is possible for reusable quartz,glass, sapphire molds to be used, since, following the production of alens, these molds can be cleaned rapidly and effectively to removeunreacted materials and other residues, using water or a suitablesolvent, and can be dried with air. Reusable molds can also be made of acyclic olefin copolymer, such as for example, Topas® COC grade 8007-S10(clear amorphous copolymer of ethylene and norbornene) from Ticona GmbHof Frankfurt, Germany and Summit, N.J., Zeonex® and Zeonor® from ZeonChemicals LP, Louisville, Ky. Because of the reusability of the moldhalves, a relatively high outlay can be expended at the time of theirproduction in order to obtain molds of extremely high precision andreproducibility. Since the mold halves do not touch each other in theregion of the lens to be produced, i.e. the cavity or actual mold faces,damage as a result of contact is ruled out. This ensures a high servicelife of the molds, which, in particular, also ensures highreproducibility of the contact lenses to be produced and high fidelityto the lens design.

After the fluid is dispensed into the mold, it is polymerized to producea contact lens. Crosslinking and/or polymerizing may be initiated in themold e.g. by means of actinic radiation, such as UV irradiation,ionizing radiation (e.g., gamma or X-ray irradiation). Where prepolymersof the invention are the polymerizable components in the fluidcomposition, the mold containing the fluid composition can be exposed toa spatial limitation of actinic radiation to crosslink the prepolymers.

A “spatial limitation of actinic radiation” refers to an act or processin which energy radiation in the form of rays is directed by, forexample, a mask or screen or combinations thereof, to impinge, in aspatially restricted manner, onto an area having a well definedperipheral boundary. For example, a spatial limitation of UV radiationcan be achieved by using a mask or screen that has a transparent or openregion (unmasked region) surrounded by a UV impermeable region (maskedregion), as schematically illustrated in FIGS. 1-9 of U.S. Pat. No.6,627,124 (herein incorporated by reference in its entirety). Theunmasked region has a well defined peripheral boundary with the unmaskedregion. The energy used for the crosslinking is radiation energy,especially UV radiation, gamma radiation, electron radiation or thermalradiation, the radiation energy preferably being in the form of asubstantially parallel beam in order on the one hand to achieve goodrestriction and on the other hand efficient use of the energy.

What is notable is that the crosslinking according to the invention maybe effected in a very short time, e.g. in ≦60 minutes, advantageously in≦20 minutes, preferably in ≦10 minutes, most preferably in ≦5 minutes,particularly preferably in 1 to 60 seconds and most particularly in 1 to30 seconds.

What is also notable is that the contact lenses according to theinvention can be produced from one or more radiation-curable prepolymersof the invention in a very simple and efficient way compared with theprior art. This is based on many factors. On the one hand, the startingmaterials may be acquired or produced inexpensively. Secondly, there isthe advantage that the prepolymers are surprisingly stable, so that theymay undergo a high degree of purification. There is no practical needfor subsequent purification, such as in particular complicatedextraction of unpolymerized constituents after curing lenses.Furthermore, the new polymerization method can be used to producecontact lenses with desirable mechanical and physical properties.Finally, photo-polymerization is effected within a short period, so thatfrom this point of view also the production process for the contactlenses according to the invention may be set up in an extremely economicway.

Opening of the mold so that the molded article can be removed from themold may take place in a manner known per se.

If the molded contact lens is produced solvent-free from an alreadypurified prepolymer according to the invention, then after removal ofthe molded lens, it is not normally necessary to follow up withpurification steps such as extraction. This is because the prepolymersemployed do not contain any undesired constituents of low molecularweight; consequently, the crosslinked product is also free orsubstantially free from such constituents and subsequent extraction canbe dispensed with. Accordingly, the contact lens can be directlytransformed in the usual way, by hydration, into a ready-to-use contactlens. Appropriate embodiments of hydration are known to the personskilled in the art, whereby ready-to-use contact lenses with very variedwater content may be obtained. The contact lens is expanded, forexample, in water, in an aqueous salt solution, especially an aqueoussalt solution having an osmolarity of about 200 to 450 milli-osmole in1000 ml (unit: mOsm/ml), preferably about 250 to 350 mOsm/l andespecially about 300 mOsm/l, or in a mixture of water or an aqueous saltsolution with a physiologically compatible polar organic solvent, e.g.glycerol. Preference is given to expansions of the article in water orin aqueous salt solutions.

If the molded contact lens is produced from an aqueous solution of analready purified prepolymer according to the invention, then thecrosslinked product also does not contain any troublesome impurities. Itis therefore not necessary to carry out subsequent extraction. Sincecrosslinking is carried out in an essentially aqueous solution, it isadditionally unnecessary to carry out subsequent hydration. The contactlenses obtained by this process are therefore notable, according to anadvantageous embodiment, for the fact that they are suitable for theirintended usage without extraction. By intended usage is understood, inthis context, that the contact lenses can be used in the human eye.

Similarly, if the molded contact lens is produced from a solventsolution of an already purified prepolymer according to the invention,it is not necessary to carry out subsequent extraction, but instead ofhydration process to replace the solvent.

The molded contact lenses can further subject to further processes, suchas, for example, surface treatment, sterilization, and the like.

In another aspect, the invention provides a prepolymer suitable formaking soft hydrogel contact lenses. The prepolymer of the inventioncomprises multiple first propagating groups each capable of undergoingphoto-induced step-growth polymerization in the presence of or in theabsence of second propagating groups each co-reactive with the firstpropagating group in a photo-induced step-growth polymerization, whereinthe prepolymer is capable of being crosslinked under actinic irradiationto form a hydrogel material in the absence of any vinylic monomer and/orany compound having from two to eight acryloyl or methacryloyl groupsand having a molecular weight of less than 700 Daltons.

In a preferred embodiment, a prepolymer suitable for making softhydrogel contact lenses comprises: multiple thiol groups, multipleene-containing groups of formula (I), (II) or (III), multiple cinnamicacid moieties of formula (IV), multiple dialkylalmeimide groups offormula (V), or combinations thereof, wherein the prepolymer is capableof being crosslinked under actinic irradiation to form a hydrogelmaterial in the absence of any vinylic monomer and/or any compoundhaving from two to eight acryloyl or methacryloyl groups and having amolecular weight of less than 700 Daltons.

As described above, a prepolymer of the invention is obtained from acopolymer with pendant or terminal functional groups by covalentlyattaching thiol groups, ene-containing groups of formula (I), (II) or(III), cinnamic acid moieties of formula (IV), dialkylalmeimide groupsof formula (V) to the copolymer through the pendant or terminalfunctional groups. Preferably, the functional group is selected from thegroup consisting of hydroxyl groups (—OH), primary amino groups (—NH₂),secondary amino groups (—NHR), carboxylic groups (—COOH), epoxy groups,aldehyde groups (—CHO), amide groups (—CONH₂), acid halide groups (—COX,X═Cl, Br, or I), isothiocyanate groups, isocyanate groups, halide groups(—X, X═Cl, Br, or I), acid anhydride groups, and combinations thereof.Preferably, the copolymer with pendant or terminal functional groupscomprises at least one siloxane units.

In a preferred embodiment, the copolymer with pendant or terminalfunctional groups is obtained by copolymerization of a compositioncomprising (1) at least one hydrophilic vinylic monomer (i.e., havingone ethylenically unsaturated double bond), (2) at least onesilicone-containing monomer having one ethylenically unsaturated doublebond, at least one siloxane-containing macromer having one ethylenicallyunsaturated double bond, at least one siloxane-containing macromerhaving two or more ethylenically unsaturated double bonds, apolysiloxane having two or more ethylenically unsaturated double bonds,a perfluoroalkyl polyether having two or more ethylenically unsaturateddouble bonds, a polysiloxane/perfluoroalkyl polyether block copolymerhaving two or more ethylenically unsaturated double bonds, or acombination of two or more thereof, (3) optionally at least onehydrophobic vinylic monomer (i.e., having one ethylenically unsaturateddouble bond); and (4) optionally one or more hydrophilic prepolymershaving multiple acryloyl or methacryloyl groups, provided that at leastone of components (1)-(4) further comprises at least one functionalgroup through which a thiol group, an ene-containing group, a cinnamicacid moiety, or an dialkylalmeimide group can be covalently linked tothe obtained copolymer.

In another preferred embodiment, the copolymer with pendant or terminalfunctional groups is obtained by copolymerization of a compositioncomprising (1) at least one hydrophilic vinylic monomer, (2) at leastone silicone-containing monomer having one ethylenically unsaturateddouble bond, at least one siloxane-containing macromer having oneethylenically unsaturated double bond, at least one siloxane-containingmacromer having two or more ethylenically unsaturated double bonds, apolysiloxane having two or more ethylenically unsaturated double bonds,a perfluoroalkyl polyether two or more ethylenically unsaturated doublebonds, a polysiloxane/perfluoroalkyl polyether block copolymer two ormore ethylenically unsaturated double bonds, or a combination of two ormore thereof, (3) optionally at least one hydrophobic vinylic monomer;(4) optionally one or more hydrophilic prepolymers having multipleacryloyl or methacryloyl groups, and (5) at least one chain transferagent having a functional group.

In another preferred embodiment, the copolymer is a fluorine-containingcopolymer with pendant or terminal functional groups which is acopolymerization product of a polymerizable composition. The compositioncomprises (a) at least one fluorine-containing vinylic monomer, (b) atleast one hydrophilic vinylic monomer, (c) at least one functionalizingvinylic monomer containing at least one functional group, and (d) atleast one silicone-containing monomer having one ethylenicallyunsaturated double bond, at least one siloxane-containing macromerhaving one ethylenically unsaturated double bond, at least onesiloxane-containing macromer having two or more ethylenicallyunsaturated double bonds, a polysiloxane having two or moreethylenically unsaturated double bonds, a perfluoroalkyl polyether twoor more ethylenically unsaturated double bonds, apolysiloxane/perfluoroalkyl polyether block copolymer two or moreethylenically unsaturated double bonds, or a combination of two or morethereof. The polymerizable composition can also include a polymerizationinitiator (i.e., a photoinitiator or a thermal initiator), a solvent,and a chain transfer agent.

In another preferred embodiment, the fluorine-containing copolymer withpendant or terminal functional groups is a copolymerization product of apolymerizable composition, which comprises (a) at least onefluorine-containing vinylic monomer, (b) at least one hydrophilicvinylic monomer, (c) at least one silicone-containing monomer having oneethylenically unsaturated double bond, at least one siloxane-containingmacromer having one ethylenically unsaturated double bond, at least onesiloxane-containing macromer having two or more ethylenicallyunsaturated double bonds, a polysiloxane having two or moreethylenically unsaturated double bonds, a perfluoroalkyl polyether twoor more ethylenically unsaturated double bonds, apolysiloxane/perfluoroalkyl polyether block copolymer two or moreethylenically unsaturated double bonds, or a combination of two or morethereof, and (d) at least one chain transfer agent having a functionalgroup. The polymerizable composition can also include a polymerizationinitiator (i.e., a photoinitiator or a thermal initiator), a solvent,and a chain transfer agent.

Nearly any hydrophilic vinylic monomer can be used in the fluidcomposition of the invention. Suitable hydrophilic monomers are, withoutthis being an exhaustive list, hydroxyl-substituted lower alkyl (C₁ toC₈) acrylates and methacrylates, acrylamide, methacrylamide, (lowerallyl)acrylamides and -methacrylamides, ethoxylated acrylates andmethacrylates, hydroxyl-substituted (lower alkyl)acrylamides and-methacrylamides, hydroxyl-substituted lower alkyl vinyl ethers, sodiumvinylsulfonate, sodium styrenesulfonate,2-acrylamido-2-methylpropanesulfonic acid, N-vinylpyrrole,N-vinyl-2-pyrrolidone, 2-vinyloxazoline,2-vinyl-4,4′-dialkyloxazolin-5-one, 2- and 4-vinylpyridine, vinylicallyunsaturated carboxylic acids having a total of 3 to 5 carbon atoms,amino(lower alkyl)—(where the term “amino” also includes quaternaryammonium), mono(lower alkylamino)(lower alkyl) and di(loweralkylamino)(lower alkyl)acrylates and methacrylates, allyl alcohol andthe like.

Among the preferred hydrophilic vinylic monomers areN,N-dimethylacrylamide (DMA), 2-hydroxyethylmethacrylate (HEMA),2-hydroxyethyl acrylate (HEA), hydroxypropyl acrylate, hydroxypropylmethacrylate (HPMA), trimethylammonium 2-hydroxy propylmethacrylatehydrochloride, dimethylaminoethyl methacrylate (DMAEMA), glycerolmethacrylate (GMA), N-vinyl-2-pyrrolidone (NVP),dimethylaminoethylmethacrylamide, acrylamide, methacrylamide, allylalcohol, vinylpyridine, N-(1,1 dimethyl-3-oxobutyl)acrylamide, acrylicacid, and methacrylic acid.

Suitable hydrophobic vinylic monomers include, without limitation,C₁-C₁₈-alkylacrylates and -methacrylates, C₃-C₁₈ alkylacrylamides and-methacrylamides, acrylonitrile, methacrylonitrile,vinyl-C₁-C₁₈-alkanoates, C₂-C₁₈-alkenes, C₂-C₁₈-halo-alkenes, styrene,C₁-C₆-alkylstyrene, vinylalkylethers in which the alkyl moiety has 1 to6 carbon atoms, C₂-C₁₀-perfluoralkyl-acrylates and -methacrylates orcorrespondingly partially fluorinated acrylates and methacrylates,C₃-C₁₂-perfluoralkyl-ethyl-thiocarbonylaminoethyl-acrylates and-methacrylates, acryloxy and methacryloxy-alkylsiloxanes,N-vinylcarbazole, C₁-C₁₂-alkylesters of maleic acid, fumaric acid,itaconic acid, mesaconic acid and the like. Preference is given e.g. toC₁-C₄-alkylesters of vinylically unsaturated carboxylic acids with 3 to5 carbon atoms or vinylesters of carboxylic acids with up to 5 carbonatoms.

Examples of preferred hydrophobic vinylic monomers includemethylacrylate, ethyl-acrylate, propylacrylate, isopropylacrylate,cyclohexylacrylate, 2-ethylhexylacrylate, methylmethacrylate,ethylmethacrylate, propylmethacrylate, vinyl acetate, vinyl propionate,vinyl butyrate, vinyl valerate, styrene, chloroprene, vinyl chloride,vinylidene chloride, acrylonitrile, 1-butene, butadiene,methacrylonitrile, vinyl toluene, vinyl ethyl ether,perfluorohexylethyl-thio-carbonyl-aminoethyl-methacrylate, isobornylmethacrylate, trifluoroethyl methacrylate, hexafluoro-isopropylmethacrylate, hexafluorobutyl methacrylate,tris-trimethylsilyloxy-silyl-propyl methacrylate,3-methacryloxypropyl-pentamethyl-disiloxane andbis(methacryloxypropyl)-tetramethyl-disiloxane.

Any know suitable vinylic monomer containing at least one functionalgroup can be used in the present invention. Preferred examples of suchvinylic monomers includes methacrylic acid (MAA), acrylic acid,glycidylmethacrylate, glycidylacrylate, HEMA, HEA, methacrylicanhydride, N-hydroxymethylacrylamide (NHMA), 2-bromoethylmethacrylate,and vinylbenzylchloride.

Any silicone-containing vinylic monomers can be used in the invention.Examples of silicone-containing vinylic monomers include, withoutlimitation, methacryloxyalkylsiloxanes, 3-methacryloxypropylpentamethyldisiloxane,bis(methacryloxypropyl)tetramethyl-disiloxane, monomethacrylatedpolydimethylsiloxane, monoacrylated polydimethylsiloxane,mercapto-terminated polydimethylsiloxane,N-[tris(trimethylsiloxy)silylpropyl]acrylamide,N-[tris(trimethylsiloxy)silylpropyl]methacrylamide, andtristrimethylsilyloxysilylpropyl methacrylate (TRIS),N-[tris(trimethylsiloxy)silylpropyl]methacrylamide (“TSMAA”),N-[tris(trimethylsiloxy)silylpropyl]acrylamide (“TSAA”), 2-propenoicacid, 2-methyl-,2-hydroxy-3-[3-[1,3,3,3-tetramethyl-1-[(trimethylsilyl)oxy]disiloxanyl]propoxy]propyl ester (which can also be named(3-methacryloxy-2-hydroxypropyloxy)propylbis(trimethylsiloxy)methylsilane),(3-methacryloxy-2-hydroxypropyloxy)propyltris(trimethylsiloxy)silane,bis-3-methacryloxy-2-hydroxypropyloxypropyl polydimethylsiloxane,3-methacryloxy-2-(2-hydroxyethoxy)propyloxy)propylbis(trimethylsiloxy)methylsilane,N,N,N′,N′-tetrakis(3-methacryloxy-2-hydroxypropyl)-alpha,omega-bis-3-aminopropyl-polydimethylsiloxane,polysiloxanylalkyl (meth)acrylic monomers, silicone-containing vinylcarbonate or vinyl carbamate monomers (e.g.,1,3-bis[4-vinyloxycarbonyloxy)but-1-yl]tetramethyl-disiloxane;3-(trimethylsilyl), propyl vinyl carbonate,3-(vinyloxycarbonylthio)propyl-[tris(trimethylsiloxy)silane],3-[tris(trimethylsiloxy)silyl] propylvinyl carbamate,3-[tris(trimethylsiloxy)silyl] propyl allyl carbamate,3-[tris(trimethylsiloxy)silyl]propyl vinyl carbonate,t-butyldimethylsiloxyethyl vinyl carbonate; trimethylsilylethyl vinylcarbonate, and trimethylsilylmethyl vinyl carbonate). A preferredsiloxane-containing monomer is TRIS, which is referred to3-methacryloxypropyltris(trimethylsiloxy) silane, and represented by CASNo. 17096-07-0. The term “TRIS” also includes dimers of3-methacryloxypropyltris(trimethylsiloxy) silane. Monomethacrylated ormonoacrylated polydimethylsiloxanes of various molecular weight could beused. Dimethacrylated or Diacrylated polydimethylsiloxanes of variousmolecular weight could also be used.

Any suitable siloxane-containing macromer with ethylenically unsaturatedgroup(s) can be used to produce a silicone hydrogel material. Aparticularly preferred siloxane-containing macromer is selected from thegroup consisting of Macromer A, Macromer B, Macromer C, and Macromer Ddescribed in U.S. Pat. No. 5,760,100, herein incorporated by referencein its entirety. Macromers could be mono or difunctionalized withacrylate, methacrylate or vinyl groups. Macromers that contain two ormore polymerizable groups (vinylic groups) can also serve as crosslinkers. Di and triblock macromers consisting of polydimethylsiloxaneand polyakyleneoxides could also be of utility. For example one mightuse methacrylate end cappedpolyethyleneoxide-block-polydimethylsiloxane-block-polyethyleneoxide toenhance oxygen permeability.

Examples of silicone-containing prepolymers include without limitationthose disclosed in US Patent Application Publication No. US 2001-0037001A1 and U.S. Pat. No. 6,039,913, which are incorporated herein byreferences in their entireties.

Preferred example of polysiloxanes having two or more ethylenicallyunsaturated double bonds, perfluoroalkyl polyethers having two or moreethylenically unsaturated double bonds, polysiloxane/perfluoroalkylpolyether block copolymers having two or more ethylenically unsaturateddouble bonds are disclosed in U.S. Pat. No. 7,091,283 (hereinincorporated by reference in its entirety.

A preferred polysiloxane having two or more ethylenically unsaturateddouble bonds is defined by formula (1)

in which (alk) is alkylene having up to 20 carbon atoms which may beinterrupted by —O—; X is —O— or —NR₃₁—, R₃₁ is hydrogen or C₁-C₆-alkyl,Q is an organic radical comprising a crosslinkable or polymerizablegroup, 80-100% of the radicals R₂₉, R₂₉′, R₂₉″, R₂₉′″, R₂₉*, R₃₀, R₃₀′and R₃₀″, independently of one another, are C₁-C₈-alkyl and 0-20% of theradicals R₂₉, R₂₉′, R₂₉″, R₂₉′″, R₂₉*, R₃₀, R₃₀′ and R₃₀″, independentlyof one another, are unsubstituted or C₁-C₄ alkyl- or C₁-C₄—alkoxy-substituted phenyl, fluoro(C₁-C₁₈-alkyl), cyano(C₁-C₁₂-alkyl),hydroxy-C₁-C₆-alkyl or amino-C₁-C₆-alkyl, x is the number 0 or 1, d₁ isan integer of from 5 to 700, d₂ is an integer from 0 to 8 if x is 0, andis 2 to 10 if x is 1, and the sum of (d₁+d₂) is from 5 to 700.

A more preferred polysiloxane having two or more ethylenicallyunsaturated double bonds is defined by formula (2)

wherein R₂₉, R₂₉′, R₃₀ and R₃₀′ are each methyl, d₁ is an integer from10 to 300, (alk) is linear or branched C₂-C₆ alkylene or a radical—(CH₂)₁₋₃—O—(CH₂)₁₋₃—, X is —O— or —NH— and Q is a radical of theformula (3), (4), (5), or (6)

Another more preferred polysiloxane having two or more ethylenicallyunsaturated double bonds is defined by formula (7)Q-(PDMS)₁-L-(PDMS)₂-Q  (7),in which (PDMS)₁ and (PDMS)₂ are, each, independently of the other, aradical of formula (8)

in which R₂₉, R₂₉′, R₃₀ and R₃₀′ are each methyl, d₁ is an integer from10 to 300, (alk) is linear or branched C₂-C₆ alkylene or a radical—(CH₂)₁₋₃—O—(CH₂)₁₋₃—, X is —O— or —NH—, wherein the weight averagemolecular weight of the segment of formula (8) is in the range of from18° to 6000; Q is an organic radical comprising a crosslinkable orpolymerizable group; and L is a difunctional linking group.

A preferred perfluoroalkyl polyether having two or more ethylenicallyunsaturated double bonds formula (9)Q-(PFPE-L)_(n-1)-PFPE-Q  (9)wherein n is ≧1, each PFPE may be the same or different and is aperfluorinated polyether of formula (10)—OCH₂CF₂O(CF₂CF₂O)_(z)(CF₂O)_(y)CF₂CH₂O—  (10)wherein the CF₂CF₂O and CF₂O units may be randomly distributed ordistributed as blocks throughout the chain and wherein z and y may bethe same or different such that the weight average molecular weight ofthe perfluoropolyether is in the range of from 500 to 4,000; wherein Lis a difunctional linking group; and wherein Q is an organic radicalcomprising a crosslinkable or polymerizable group.

A more preferred perfluoroalkyl polyether having two or moreethylenically unsaturated double bonds is defined by formula (11)Q-PFPE-Q  (11)wherein Q is an organic radical comprising a crosslinkable orpolymerizable group; PFPE is a perfluorinated polyether of formula (10)in which z and y may be the same or different such that the molecularweight of the perfluoroalkyl polyether is in the range of from 500 to2,500.

A polysiloxane/perfluoroalkyl polyether block copolymer having two ormore ethylenically unsaturated double bonds is defined by formula (12)Q-PFPE-L-M-L-PFPE-Q  (12)wherein L is a difunctional linking group; Q is an organic radicalcomprising a crosslinkable or polymerizable group; PFPE is aperfluorinated polyether of formula (10) in which z and y may be thesame or different such that the molecular weight of the perfluoroalkylpolyether is in the range of from 500 to 2,500; and M is a radical offormula (8) in which R₂₉, R₂₉′, R₃₀ and R₃₀′ are each methyl, d₁ is aninteger from 10 to 300, (alk) is linear or branched C₂-C₆ alkylene or aradical —(CH₂)₁₋₃—O—(CH₂)₁₋₃—, X is —O— or —NH—, wherein the weightaverage molecular weight of the segment of formula (8) is in the rangeof from 180 to 6000.

Examples of hydrophilic prepolymers with multiple acryloyl ormethacryloyl groups include, but are not limited to, a water-solublecrosslinkable poly(vinyl alcohol) prepolymer described in U.S. Pat. Nos.5,583,163 and 6,303,687; a water-soluble vinyl group-terminatedpolyurethane prepolymer described in U.S. Patent Application PublicationNo. 2004/0082680; derivatives of a polyvinyl alcohol, polyethyleneimineor polyvinylamine, which are disclosed in U.S. Pat. No. 5,849,841; awater-soluble crosslinkable polyurea prepolymer described in U.S. Pat.No. 6,479,587 and in U.S. Published Application No. 2005/0113549;crosslinkable polyacrylamide; crosslinkable statistical copolymers ofvinyl lactam, MMA and a comonomer, which are disclosed in EP 655,470 andU.S. Pat. No. 5,712,356; crosslinkable copolymers of vinyl lactam, vinylacetate and vinyl alcohol, which are disclosed in EP 712,867 and U.S.Pat. No. 5,665,840; polyether-polyester copolymers with crosslinkableside chains which are disclosed in EP 932,635 and U.S. Pat. No.6,492,478; branched polyalkylene glycol-urethane prepolymers disclosedin EP 958,315 and U.S. Pat. No. 6,165,408; polyalkyleneglycol-tetra(meth)acrylate prepolymers disclosed in EP 961,941 and U.S.Pat. No. 6,221,303; and crosslinkable polyallylamine gluconolactoneprepolymers disclosed in International Application No. WO 2000/31150 andU.S. Pat. No. 6,472,489.

The functional chain transfer agent is used to control the molecularweight of the resulting copolymer and to provide functionality forsubsequent addition of a thiol group, an ene-containing group, acinnamic acid moiety, a dialkylmaleimide group. The chain transfer agentmay comprise one or more thiol groups, for example two or mostpreferably one thiol group. Suitable chain transfer agents includeorganic primary thiols or mercaptans having a further functional groupsuch as, for example, hydroxy, amino, N—C₁-C₆-alkylamino, carboxy or asuitable derivative thereof. A preferred chain transfer agent is acycloaliphatic or preferably aliphatic thiol having from 2 to about 24carbon atoms and having a further functional group selected from amino,hydroxy and carboxy; accordingly, the preferred chain transfer agentsare aliphatic mercapto carboxylic acids, hydroxymercaptans oraminomercaptans. Examples of particularly preferred chain transferagents are thioglycolic acid, 2-mercaptoethanol and especially2-aminoethane thiol (cysteamine). In case of an amine or a carboxylicacid, the chain transfer agent may be in form of the free amine or acidor, preferably, in form of a suitable salt thereof, for example ahydrochloride in case of an amine or a sodium, potassium or amine saltin case of an acid. An example for a chain transfer agent having morethan one thiol group is the reaction product of one equivalent ofdiethylene triamine with about two equivalents of □-thiobutyrolactone.

Any fluorine-containing (or fluorinated) monomer can be used in theinvention. Preferably, a fluorine-containing monomer contains at least 3fluorine atoms per monomer molecule that itself contains from about 4 toabout 20, preferably from about 6 to about 15 carbon atoms, sometimesalso referred as a polyfluorinated monomer.

Preferred fluorinated monomers include2-(N-ethyl-perfluorooctanesulfonamido)-ethylacrylate (FX-13),2-(N-ethyl-perfluoro-octanesulfonamido)ethyl methacrylate (FX-14),2,2,2-trifluoroethyl methacrylate (TEM),1,1-dihydroperfluoroethylacrylate, 1H,1H,7H-dodecafluoroheptyl acrylate(DFHA), hexafluoroisopropyl acrylate, 1H,1H,2H,2H-heptadecafluorodecylacrylate, pentafluorostyrene (PFS), trifluoromethylstyrene,pentafluoroethyl acrylate, pentafluoroethyl methacrylate,hexafluoroisopropyl acrylate, hexafluoroisopropyl methacrylate (HFIPMA), methacrylate-functionalized fluorinated polyethylene oxides, andthe like. A preferred fluorinated monomer containing 3 to about 20fluorine atoms per monomer molecule is an amide or ester of acrylic acidor methacrylic acid. Particularly preferred fluorinated monomerscontaining 3 to about 20 fluorine atoms per monomer molecule are FX-13,FX-14 and 1H,1H,2H,2H-heptadecafluorodecyl acrylate that contain 13 or14 carbon atoms and PFS and HFIPMA that contain six to eight carbonatoms. The most preferred of these monomers are FX-13 and FX-14 that aresulfonamido ethyl esters of acrylic acid or methacrylic acid.

Any know suitable vinylic monomer containing at least one functionalgroup can be used as functionalizing vinylic monomer in the presentinvention. Preferred examples of such vinylic monomers includesmethacrylic acid (MAA), acrylic acid, glycidylmethacrylate,glycidylacrylate, HEMA, HEA, methacrylic anhydride,N-hydroxymethylacrylamide (NHMA), 2-bromoethylmethacrylate, andvinylbenzylchloride.

It should be understood that a vinylic monomer can be used both as ahydrophilic vinylic monomer and as a functionalizing vinylic monomer inthe polymerizable composition for preparing the silicone-containingpolymer with pendant or terminal functional groups. Preferably, thehydrophilic vinylic monomer is devoid of functional groups (e.g., DMA,NVP).

In a further aspect, the invention provides a soft hydrogel contactlens. The contact lens of the invention is obtained by polymerization ofa fluid composition, wherein the composition comprises at least oneprepolymer having multiple first propagating groups each capable ofundergoing photo-induced step-growth polymerization in the presence ofor in the absence of a step-growth-crosslinking agent having two or moresecond propagating groups each co-reactive with one of the firstpropagating group in a photo-induced step-growth polymerization,provided that the composition is substantially free of any vinylicmonomer.

In still a further aspect, the invention provides a fluid compositionfor making medical devices, preferably ophthalmic device, morepreferably soft hydrogel contact lenses. The fluid composition of theinvention comprises at least one prepolymer having multiple firstpropagating groups each capable of undergoing photo-induced step-growthpolymerization in the presence of or in the absence of astep-growth-crosslinking agent having two or more second propagatinggroups each co-reactive with one of the first propagating group in aphoto-induced step-growth polymerization, wherein the composition ischaracterized by having a low viscosity and being capable of undergoingphoto-induced step-growth polymerization to crosslink the prepolymer toform a hydrogel material, provided that the composition is substantiallyfree of any vinylic monomer.

Various embodiments of a fluid composition and prepolymers are describedabove.

Throughout this application, various publications are referenced. Thedisclosures of these publications in their entireties are herebyincorporated by reference into this application in order to more fullydescribe the compounds, compositions and methods described herein.

The previous disclosure will enable one having ordinary skill in the artto practice the invention. In order to better enable the reader tounderstand specific embodiments and the advantages thereof, reference tothe following non-limiting examples is suggested. However, the followingexamples should not be read to limit the scope of the invention.

EXAMPLE 1

Synthesis of Norbornene Carbonyl Chloride

A 500 mL sulfur flask was equipped with magnetic stirring, additionfunnel, thermometer, reflux condenser with N2-inlet adapter, and outletadapter connected to a trap immersed in a dry ice/acetone bath. 58.28 gof 2-norbornene-5-carboxylic acid (Aldrich) were charged to the reactorunder a positive flow of nitrogen, then 31.4 mL of thionyl chloride(51.32 g). 450 mL of methyl-tert-butyl ether were added, an ice bath wasapplied, and the contents of the reactor were stirred to mix and cool to3° C. 51.6 mL of triethylamine (37.45 g) and 20 mL of MTBE were chargedto the addition funnel and added dropwise to keep temperature less than10° C. On completion of the addition the ice bath was removed and theflask was stirred for one hour. The resulting suspension was filtered toremove triethylamine hydrochloride. The resulting clear yellow solutionwas reduced to an oil on a rotary evaporator and purified by fractionaldistillation at 8 mBar (fraction boiling at 62-75° C.). 72% recovery at99.13% purity was attained. The product was stored in a desiccator atroom temperature until use.

EXAMPLE 2

Synthesis of alpha-omega-diacrylamide Poly(dimethylsiloxane) 4500

In a 4-L beaker, 61.73 g of Na₂CO₃ (996 mEq), 80 g of NaCl and 1.52 kgof deionized water were mixed to dissolve. In a separate 4-L beaker, 700g of alpha, omega-aminopropyl-polydimethylsiloaxane (Shin-Etsumanufacture, MW ca. 4500, 305 mEq) were dissolved in 1000 g of hexane. A4-L reactor was equipped with overhead stirring with turbine agitatorand a 250-mL addition funnel with micro-flow controller. The twosolutions were then charged to the reactor, and mixed for 15 minuteswith heavy agitation to produce an emulsion. 36.6 g of acryloyl chloride(405 mEq) was dissolved in 100 mL of hexane and charged to the additionfunnel. The acryloyl chloride solution was added dropwise to theemulsion under heavy agitation over one hour. The emulsion was stirredfor 30 minutes on completion of the addition and then agitation wasstopped and the phases were allowed to separate overnight. The aqueousphase was decanted and the organic phase was washed twice with a mixtureof 2.0 kg of 2.5% NaCl dissolved in water. The organic phase was thendried over magnesium sulfate, filtered to 1.0 μm exclusion, andconcentrated on a rotary evaporator. The resulting oil was furtherpurified by high-vacuum drying to constant weight. Analysis of theresulting product by titration revealed 0.435 mEq/g of C═C double bonds.

EXAMPLE 3

Synthesis of alpha-omega-diacrylamide Poly(dimethylsiloxane) 2500

In a 4-L beaker, 111.1 g of Na₂CO₃ hydrate (1790 mEq), 80 g of NaCl and1.52 kg of deionized water were mixed to dissolve. In a separate 4-Lbeaker, 700 g of alpha, omega-aminopropyl-polydimethylsiloaxane(Shin-Etsu manufacture, MW ca. 2500, 560 mEq) were dissolved in 1000 gof hexane. A 4-L reactor was equipped with overhead stirring withturbine agitator and a 250-mL addition funnel with micro-flowcontroller. The two solutions were then charged to the reactor, andmixed for 15 minutes with heavy agitation to produce an emulsion. 65.89g of acryloyl chloride (728.1 mEq) was dissolved in 100 mL of hexane andcharged to the addition funnel. The acryloyl chloride solution was addeddropwise to the emulsion under heavy agitation over one hour. Theemulsion was stirred for 30 minutes on completion of the addition andthen agitation was stopped and the phases were allowed to separateovernight. The aqueous phase was decanted and the organic phase waswashed twice with 2.0 kg portions of 2.5% NaCl dissolved in water. Theorganic phase was then dried over magnesium sulfate, filtered to 1.0 μmexclusion, and concentrated on a rotary evaporator. The resulting oilwas further purified by high-vacuum drying to constant weight. Analysisof the resulting product by titration revealed 0.8 mEq/g of C═C doublebonds.

EXAMPLE 4

Synthesis of Branched Alpha-Omega-Diacrylamide Poly(Dimethylsiloxane)4500

300 g of PDMS diacrylamide generated in Example 2 were dissolved in 500mL of a mixture of 70% tetrahydrofuran and 30% isopropanol in a 2-Lroundbottom flask equipped with magnetic stirring. 5.73 g oftrimethylolpropane tris(mercaptopropionate) (Aldrich) were added and themixture was stirred to homogenize. 5.0 mL of 0.1N NaOH in methanol(Fisher) were added and the flask was stirred overnight. The followingday, the reaction mixture was sampled and titrated with 0.1N Iodinesolution (Acros); 25 μL of iodine solution turned 5 mL of reactionmixture yellow, indicating the near-complete consumption of thiol. 5.0mL of HCl in isopropanol (Fisher) were added, and the solvent wasstripped on a rotary evaporator. The resulting oil was further purifiedby high-vacuum drying to constant weight.

EXAMPLE 5

Synthesis of Semi-Telechelic Silicone Hydrogel Polymer

A 2-L jacketed reactor was equipped with a heating/chilling loop, septuminlet adapter, reflux condenser with N₂-inlet adapter, and overheadstirring. A solution was generated by dissolving 55.43 g of PDMS-DAmproduced by the procedure described in Example 2 in 150 g of 1-propanol.This solution was charged to the reactor and cooled to 8° C. Thesolution was degassed by evacuating to less than 5 mBar, holding atvacuum for 15 minutes, and then re-pressurizing with dry nitrogen. Thisdegas procedure was repeated for a total of 5 times.

In a separate 500 mL flask equipped with magnetic stirring and avacuum-inlet adapter with valve, 5.9 g of cysteamine hydrochloride wasdissolved in 300 mL of 1-propanol. In another 500 mL flask equipped withmagnetic stirring and vacuum-inlet adapter with valve, a solution of30.77 g of N,N-dimethylacrylamide (Bimax Corporation) and 7.72 g ofhydroxyethyl acrylate (Aldrich) were dissolved in 300 mL of 1-propanol.In a third flask, similarly equipped, 0.18 g ofazo-bis(isobutyronitrile) (Aldrich) was dissolved in 150 g of1-propanol. All three solutions were degassed twice by evacuation to 60mBar, holding vacuum for 5 minutes, and then re-pressurizing withnitrogen.

Under a positive flow of nitrogen, the reactor was opened and thecysteamine hydrochloride, N,N-dimethylacrylamide/hydroxyethylacrylate,and azo-bis(isobutyronitrile) solutions were charged to the reactor.Still holding at 8° C., the reactor was degassed by evacuating to lessthan 5 mBar and holding for 5 minutes, then re-pressurizing withnitrogen. A total of four degassing cycles were performed. The reactorwas then heated to 68° C. and held at temperature under nitrogen withstirring for 16 hours. The reaction mixture was then transferred to aflask and vacuum stripped at 40° C./100 m Bar on a rotary evaporator toremove 1-propanol. After the first 500 g of 1-propanol was removed, 500g of water were added slowly with stirring to create an emulsion. Theemulsion was then further stripped of 1-propanol until 200 g ofdistillate were collected. 200 g of water were again added back to theemulsion, and solvent-exchange was continued to collect a final 200 g ofdistillate. The emulsion was then diluted to 2.0 kg.

This emulsion was then charged to a 2-L reactor equipped with overheadstirring, refrigeration loop, thermometer, and the pH meter anddispensing tip of a Metrohm Model 718 STAT Titrino. The reaction mixturewas then cooled to 1° C. 1.5 g of NaHCO₃ were charged to the emulsionand stirred to dissolve. The Titrino was set to maintain pH at 9.5 byintermittent addition of 15% sodium hydroxide solution. 6.2 mL ofacryloyl chloride was then added over one hour using a syringe pump. Theemulsion was stirred for another hour, then the Titrino was set toneutralize the reaction mixture by addition of a 15% solution ofhydrochloric acid. The emulsion was then drained from the reactor,diluted to 3.5 L and filtered to 16 μm exclusion. The emulsion waspurified by diafiltration (nominal molecular weight cut-off, 10,000 D)with deionized water until the permeate conductance was below 2.5 μS/cm,and polymer was isolated by lyophilization.

EXAMPLE 6

Comparative Formulation

Polymer from Example 5 were dissolved in approximately 200 mL of1-propanol, concentrated to ca. 70 g total solution weight, and filteredto 0.45 μm exclusion. 106.71 g of solution at 13.87% solids wererecovered. 3.702 g of a 1% solution of2-hydroxy-4′-hydroxyethyl-2-methylpropiophenone (IRGACURE®-2959, CibaSpecialty Chemicals) was added, and then the solution was concentratedto a final weight of 22.77 g (65.0% solids).

EXAMPLE 7 Comparative Lens Casting

The formulation of Example 6 was used to cast lenses as follows. 200 mgof the formulation was dosed into poly(propylene) molds and the moldswere closed. The molds were then irradiated for 36 sec with anultraviolet light source having an intensity of 2.18 mW/cm². The moldswere then opened, and the mold halves which had a lens attached weresoaked in a mixture of 80% isopropanol, 20% water (v/v) overnight. Thelenses were rinsed off the molds with this solvent mixture, then rinsedtwice for 2 hrs. each in fresh aliquots of isopropanol/water mixture.The lenses were drained then hydrated by immersion in deionized water.They were then rinsed three times for 2 h apiece in pure water (3.0mL/lens).

EXAMPLE 8

Formulation of the Invention

4.0 g of formulation from Example 6 were weighed into a syringe. 0.0215g of trimethylolpropane tris(mercaptopropionate) and 0.0486 g of1,6-dithiohexane were added and the formulation was stirred for fiveminutes with a steel spatula. The formulation was then dosed intopoly(propylene) molds and the molds were closed. The molds were thenirradiated for 36 sec with an ultraviolet light source having anintensity of 2.18 mW/cm². The molds were then opened, and the moldhalves which had a lens attached were soaked in a mixture of 80%isopropanol, 20% water (v/v) overnight. The lenses were rinsed off themolds with this solvent mixture, then rinsed twice for 2 hrs. each infresh aliquots of isopropanol/water mixture. The lenses were drainedthen hydrated by immersion in deionized water. They were then rinsedthree times for 2 h apiece in pure water (3.0 mL/lens).

EXAMPLE 9

Synthesis of Semi-Telechelic Silicone Hydrogel Polymer

A 2-L jacketed reactor was equipped with a heating/chilling loop, septuminlet adapter, reflux condenser with N₂-inlet adapter, and overheadstirring. A solution was generated by dissolving 62.97 g of PDMS-DAmproduced by the procedure described in Example 4 in 150 g of 1-propanol.This solution was charged to the reactor and cooled to 8° C. Thesolution was degassed by evacuating to less than 5 mBar, holding atvacuum for 15 minutes, and then re-pressurizing with dry nitrogen. Thisdegas procedure was repeated for a total of 5 times.

In a separate 500 mL flask equipped with magnetic stirring and avacuum-inlet adapter with valve, 2.72 g of cysteamine hydrochloride wasdissolved in 300 mL of 1-propanol. In another 500 mL flask equipped withmagnetic stirring and vacuum-inlet adapter with valve, a solution of27.39 g of N,N-dimethylacrylamide (Bimax Corporation) and 6.84 g ofhydroxyethyl acrylate (Aldrich) were dissolved in 300 mL of 1-propanol.In a third flask, similarly equipped, 0.19 g ofazo-bis(isobutyronitrile) (Aldrich) was dissolved in 150 g of1-propanol. All three solutions were degassed twice by evacuation to 60mBar, holding vacuum for 5 minutes, and then re-pressurizing withnitrogen.

Under a positive flow of nitrogen, the reactor was opened and thecysteamine hydrochloride, N,N-dimethylacrylamide/hydroxyethylacrylate,and azo-bis(isobutyronitrile) solutions were charged to the reactor.Still holding at 8° C., the reactor was degassed by evacuating to lessthan 5 mBar and holding for 5 minutes, then re-pressurizing withnitrogen. A total of four degassing cycles were performed. The reactorwas then heated to 68° C. and held at temperature under nitrogen withstirring for 16 hours. The reaction mixture was then transferred to aflask and vacuum stripped at 40° C./100 mBar on a rotary evaporator toremove 1-propanol. After the first 500 g of 1-propanol was removed, 500g of water were added slowly with stirring to create an emulsion. Theemulsion was then further stripped of 1-propanol until 200 g ofdistillate were collected. 200 g of water were again added back to theemulsion, and solvent-exchange was continued to collect a final 200 g ofdistillate. The emulsion was then diluted to 2.0 kg and purified bydiafiltration (nominal molecular weight cut-off, 10,000 D) withdeionized water until the permeate conductance was below 2.5 μS/cm. Thisamine-terminal polymer was isolated by lyophilization.

Approximately 50 g of the polymer was then redissolved intetrahydrofuran, and the amine equivalence was determined by titration.16.2 mEq of amine were found. 3.10 g of 50% NaOH (aq) were added to thesolution in a roundbottom flask equipped with magnetic stirring. Thecontents of the flask were cooled by means of an ice bath. 2.53 g of theacid chloride synthesized in Example 1 were diluted to 25 mL withanhydrous THF. This was added dropwise to the reaction mixture over onehour. The ice bath was removed and the reaction mixture wassolvent-exchanged to water by stripping 350 mL of solvent, back-adding350 g of deionized water, and then twice more stripping 250 mL ofsolvent and back adding 250 mL of water, for a total of 850 mL of water.The emulsion was then diluted to 2 L and filtered to 16 μm exclusion.The emulsion was purified by diafiltration (nominal molecular weightcut-off, 10,000 D) with deionized water until the permeate conductancewas below 2.5 μS/cm, and polymer was isolated by lyophilization. Thepolymer had 0.142 mEq/g of norbornene double bonds as determined by NMR.

EXAMPLE 10

Formulation of the Invention

Polymer/Irgacure formulation. 10.0 g of polymer from Example 9 wereweighed into an amber flask. 100 g of 1-propanol were added and theflask was swirled to dissolve. The solution was filtered through aWhatman glass fiber GF/B filter paper. The solids content of thesolution was measured on a halogen moisture analyzer. To the 116.32 g ofsolution at 8.27% solids, 2.405 g of Irgacure-2959 was added and thesolution was concentrated to a total weight of 12.33 g.

Stock solutions. Stock solutions of 1,6-hexanedithiol andtrimethylolpropane tris(mercaptopropionate) were prepared by diluting3.912 g of 1,6-hexanedithiol and 3.559 g of trimethylolpropanetris(mercaptopropionate) respectively to 10 mL with n-methylpyrrolidone.

Lens formulation: 65.4 μL of the 1,6-hexanedithiol stock solution, 360μL of trimethylolpropane tris(mercaptopropionate) stock solution, and2.4 g of 1-propanol were added to the polymer/Irgacure formulation andstirred for five minutes with a steel spatula.

Lens Preparation: A lens formulation was then dosed into poly(propylene)molds and the molds were closed. The molds were then irradiated for 10sec with an ultraviolet light source having an intensity of 2.18 mW/cm².The molds were then opened, and the mold halves which had a lensattached were soaked in a mixture of 80% isopropanol, 20% water (v/v)overnight. The lenses were rinsed off the molds with this solventmixture, then rinsed twice for 2 hrs. each in fresh aliquots ofisopropanol/water mixture. The lenses were drained then hydrated byimmersion in deionized water. They were then rinsed three times for 2 hapiece in pure water (3.0 mL/lens).

Obtained lenses are tested for their tear resistance (manually). Resultsare shown in Table 1.

TABLE 1 Example # Cure type Color Tensile Properties 7 Free-radicalpropagation Colorless Stiff, brittle lens 8 Acrylamide thiol-ene Slightyellow Soft, elastic 10 Norbornene thiol-ene Colorless Soft, elasticlens

Example 11 Synthesis of Semi-Telechelic Silicone Hydrogel Polymer

A 2-L jacketed reactor was equipped with a heating/chilling loop, septuminlet adapter, reflux condenser with N₂-inlet adapter, and overheadstirring. A solution was generated by dissolving 125.93 g of PDMS-DAmproduced by the procedure described in Example 4 in 555 g of 1-propanol.This solution was charged to the reactor and cooled to 8° C. Thesolution was degassed by evacuating to less than 5 mBar, holding atvacuum for 15 minutes, and then re-pressurizing with dry nitrogen. Thisdegas procedure was repeated for a total of 5 times.

In a separate 1000 mL flask equipped with magnetic stirring and avacuum-inlet adapter with valve, 5.44 g of cysteamine hydrochloride wasdissolved in 280 g of 1-propanol. In another 1000 mL flask equipped withmagnetic stirring and vacuum-inlet adapter with valve, a solution of54.79 g of N,N-dimethylacrylamide (Bimax Corporation) and 13.68 g ofhydroxyethyl acrylate (Aldrich) were dissolved in 280 g of 1-propanol.In a third flask, similarly equipped, 0.37 g ofazo-bis(isobutyronitrile) (Aldrich) was dissolved in 37 g of 1-propanol.All three solutions were degassed twice by evacuation to 60 mBar,holding vacuum for 5 minutes, and then re-pressurizing with nitrogen.

Under a positive flow of nitrogen, the reactor was opened and thecysteamine hydrochloride, N,N-dimethylacrylamide/hydroxyethylacrylate,and azo-bis(isobutyronitrile) solutions were charged to the reactor.Still holding at 8° C., the reactor was degassed by evacuating to lessthan 5 mBar and holding for 5 minutes, then re-pressurizing withnitrogen. A total of four degassing cycles were performed. The reactorwas then heated to 68° C. and held at temperature under nitrogen withstirring for 16 hours. The reaction mixture was then transferred to aflask and vacuum stripped at 40° C./100 mBar on a rotary evaporator toremove 1-propanol. After the first 672 g of 1-propanol was removed, 800g of water were added slowly with stirring to create an emulsion. Theemulsion was then further stripped of 1-propanol until 769 g ofdistillate were collected. 800 g of water were again added back to theemulsion, and solvent-exchange was continued to collect a final 225 g ofdistillate. The emulsion was then diluted to 3.0 kg and purified bydiafiltration (nominal molecular weight cut-off, 10,000 D) withdeionized water until the permeate conductance was below 2.5 μS/cm. Thisamine-terminal polymer was isolated by lyophilization.

95.0 g of the polymer was then dissolved in 800 mL of anhydrous,inhibitor-free tetrahydrofuran. 20 g of magnesium sulfate were added andthe flask was stirred for 30 minutes. The suspension was filtered to 1.2μm exclusion with a glass-fiber filter paper and then titrated tomeasure the amine equivalence. 950 g of solution with a totalequivalence of 7.5 mEq amine were recovered. 1.68 g ofdiazabicyclooctane (15.0 mEq) were added to the flask containing thesolution and stirred to dissolve. 2.35 g of the acid chloride of Example1 (15 mEq) were then diluted to 4 mL with anhydrous, inhibitor-free THFand added dropwise with a pipet. The flask was then equipped with areflux condenser with N2-inlet adapter and refluxed for three hours. Thereaction mixture was then diluted to 1.5 L with deionized water. THF wasthen removed from the solution on a rotary evaporator by stripping500-600 mL of fluid, back-adding water, and continuing to stripdistillate and back-add deionized water until an essentially aqueousemulsion remained. The emulsion was then diluted to 2.0 kg and purifiedby diafiltration (nominal molecular weight cut-off, 10,000 D) withdeionized water until the permeate conductance was below 2.5 μS/cm andno odor of norbornene carboxylic acid was detected in the permeate. Thisnorbornene-terminal polymer was isolated by lyophilization, and wasanalyzed and found to possess 0.079 mEq/g of double bonds fromnorbornene.

EXAMPLE 12

In a 4-L beaker, 24.13 g of Na2CO3 (389 mEq), 80 g of NaCl and 1.52 kgof deionized water were mixed to dissolve. In a separate 4-L beaker, 700g of alpha-omega-aminopropyl-polydimethylsiloaxane (Shin-Etsumanufacture, MW ca. 11500, 123 mEq) were dissolved in 1000 g of hexane.A 4-L reactor was equipped with overhead stirring with turbine agitatorand a 250-mL addition funnel with micro-flow controller. The twosolutions were then charged to the reactor, and mixed for 15 minuteswith heavy agitation to produce an emulsion. 14.5 g of acryloyl chloride(160.2 mEq) was dissolved in 100 mL of hexane and charged to theaddition funnel. The acryloyl chloride solution was added dropwise tothe emulsion under heavy agitation over one hour. The emulsion wasstirred for 30 minutes on completion of the addition and then agitationwas stopped and the phases were allowed to separate overnight. Theaqueous phase was decanted and the organic phase was washed twice with amixture of 2.0 kg of 2.5% NaCl dissolved in water. The organic phase wasthen dried over magnesium sulfate, filtered to 1.0 μm exclusion, andconcentrated on a rotary evaporator. The resulting oil was furtherpurified by high-vacuum drying to constant weight. Analysis of theresulting product by titration revealed 0.175 mEq/g of C═C double bonds.

EXAMPLE 13

Synthesis of Semi-Telechelic Silicone Hydrogel Polymer

A 2-L jacketed reactor was equipped with a heating/chilling loop, septuminlet adapter, reflux condenser with N₂-inlet adapter, and overheadstirring. A solution was generated by dissolving 54.86 g of PDMS-DAmproduced by the procedure described in Example 12 and 6.24 g of thePDMS-DAm produced by Example 2 in 200 g of 1-propanol. This solution wascharged to the reactor and cooled to 8° C. The solution was degassed byevacuating to less than 5 mBar, holding at vacuum for 15 minutes, andthen re-pressurizing with dry nitrogen. This degas procedure wasrepeated for a total of 5 times.

In a separate 500 mL flask equipped with magnetic stirring and avacuum-inlet adapter with valve, 2.84 g of cysteamine hydrochloride wasdissolved in 140 g of 1-propanol. In another 500 mL flask equipped withmagnetic stirring and vacuum-inlet adapter with valve, a solution of28.84 g of N,N-dimethylacrylamide (Bimax Corporation) and 7.21 g ofhydroxyethyl acrylate (Aldrich) were dissolved in 210 g of 1-propanol.In a 125 mL flask, similarly equipped, 0.14 g ofazo-bis(isobutyronitrile) (Aldrich) was dissolved in 14 g of 1-propanol.And in a fourth, 100 mL flask, 0.72 g of hydroxyethyl acrylate and 2.88g of N,N-dimethylacrylamide were dissolved in 21 g of 1-propanol. Allfour solutions were degassed twice by evacuation to 60 mBar, holdingvacuum for 5 minutes, and then re-pressurizing with nitrogen.

Under a positive flow of nitrogen, the reactor was opened and thecysteamine hydrochloride and the larger of the twoN,N-dimethylacrylamide/hydroxyethylacrylate solutions were charged tothe reactor. Still holding at 8° C., the reactor was degassed byevacuating to less than 5 mBar and holding for 5 minutes, thenre-pressurizing with nitrogen. A total of four degassing cycles wereperformed. The solution containing 0.72 g of hydroxyethyl acrylate and2.88 g of N,N-dimethylacrylamide was charged to the reservoir of anAlltech 301 HPLC pump equipped with an Alltech 590516 in-line degassingunit. The outlet was positioned to return fluid to the reservoir, andthe pump was run at a rate of 0.146 mL/min for 30 minutes to furtherdeoxygenate the solution.

The reactor was then heated to 68° C., and the HPLC pump was stopped andits outlet affixed to drop fluid into the reaction mixture withoutcontacting the walls of the vessel. When at temperature, theazobis(isobutyronitrile) solution was injected into the reactor with asyringe and the HPLC pump was started. The solution was dosed to thereactor over three hours, and then 10 mL of filtered propanol was runthrough the HPLC lines into the reactor as a rinse. The reactor was thencooled to room temperature.

The reaction mixture was then transferred to a flask and vacuum strippedat 40° C./100 mBar on a rotary evaporator to remove 1-propanol. Afterthe first 344 g of 1-propanol was removed, 500 g of water were addedslowly with stirring to create an emulsion. The emulsion was thenfurther stripped of 1-propanol until 473 g of distillate were collected.600 g of water were again added back to the emulsion, andsolvent-exchange was continued to collect a final 150 g of distillate.The emulsion was then diluted to 2.0 kg and purified by diafiltration(nominal molecular weight cut-off, 10,000 D) with deionized water untilthe permeate conductance was less than 3.0 μS/cm². The material was thenisolated by lyophilization.

40 g of the polymer thus produced was dissolved in approximately 400 mLof anhydrous, inhibitor-free tetrahydrofuran. 20 g of magnesium sulfatewere added and the flask was stirred for 30 minutes. The suspension wasfiltered to 1.2 μm exclusion with a glass-fiber filter paper and thentitrated to measure the amine equivalence. 398 g of solution with atotal equivalence of 3.58 mEq amine were recovered. 0.80 g ofdiazabicyclooctane (7.16 mEq) were added to the flask containing thesolution and stirred to dissolve. 1.12 g of the acid chloride of Example1 (7.16 mEq) were then diluted to 4 mL with anhydrous, inhibitor-freeTHF and added dropwise with a pipet. The flask was then equipped with areflux condenser with N₂-inlet adapter and refluxed for three hours. Thereaction mixture was then diluted with 200 mL of deionized water. THFwas then removed from the solution on a rotary evaporator by stripping150-200 mL of fluid, back-adding water, and continuing to stripdistillate and back-add deionized water until an essentially aqueousemulsion remained. The emulsion was then diluted to 2.0 kg and purifiedby diafiltration (nominal molecular weight cut-off, 10,000 D) withdeionized water until the permeate conductance was below 2.5 μS/cm andno odor of norbornene carboxylic acid was detected in the permeate. Thisnorbornene-terminal polymer was isolated by lyophilization, and wasanalyzed and found to possess 0.09 mEq/g of double bonds fromnorbornene.

EXAMPLE 14

10 g of polymer from Example 9 were dissolved in approximately 200 mL of1-propanol and filtered to 0.45 μm exclusion. 148.1 g of solution at6.74% solids were recovered. 2.5 g of a 1% solution of2-hydroxy-4′-hydroxyethyl-2-methylpropiophenone (IRGACURE®-2959, CibaSpecialty Chemicals) was added, and then the solution was concentratedto a final weight of 15.32 g (65.0% solids).

EXAMPLE 15

26.22 g of polymer from Example 13 were dissolved in approximately 200mL of 1-propanol and filtered to 0.45 μm exclusion. 187.78 g of solutionat 13.65% solids were recovered. 6.45 g of a 1% solution of2-hydroxy-4′-hydroxyethyl-2-methylpropiophenone (IRGACURE®-2959, CibaSpecialty Chemicals) was added, and then the solution was concentratedto a final weight of 36.63 g (70.0% solids).

EXAMPLE 16

Approximately 75 g of polymer from Example 11 were dissolved inapproximately 400 mL of 1-propanol and filtered to 0.45 μm exclusion.435.24 g of solution at 14.24% solids were recovered. 15.5 g of a 1%solution of 2-hydroxy-4′-hydroxyethyl-2-methylpropiophenone(IRGACURE®-2959, Ciba Specialty Chemicals) was added, and then thesolution was concentrated to a final weight of 95.35 g (65.0% solids).

EXAMPLE 17

5.0 g of the formulation of Example 14 and 5.0 g of the formulation ofExample 15 were weighed into an amber vial. 1.14 g of alpha-omegadithio(polydimethylsiloxane) (MW 3,000 D, Shin-Etsu Co.) were added andthe flask was stirred with a metal spatula for 5 minutes. Theformulation was transferred to dosing syringes. The formulation was thenused to cast lenses as follows. 200 mg of the formulation was dosed intopoly(propylene) molds and the molds were closed. The molds were thenirradiated for 40 sec with an ultraviolet light source having anintensity of 1.82 MW/cm². The molds were then opened, and the moldhalves which had a lens attached were soaked in a mixture of 80%isopropanol, 20% water (v/v) overnight. The lenses were rinsed off themolds with this solvent mixture, then rinsed twice for 2 hrs. each infresh aliquots of isopropanol/water mixture. The lenses were drainedthen hydrated by immersion in deionized water. They were then rinsedthree times for 2 h apiece in pure water (3.0 mL/lens).

EXAMPLE 18

4.0 g of the formulation of Example 14 and 4.0 g of the formulation ofExample 15 were weighed into an amber vial. 0.48 g of alpha-omegadithio(polydimethylsiloxane) (MW 3,000 D, Shin-Etsu Co.) and 0.634 g ofPoly(dimethylsiloxane)-co-(mercaptopropyl-methysiloxane) were added andthe flask was stirred with a metal spatula for 5 minutes. Theformulation was transferred to dosing syringes. The formulation was thenused to cast lenses as follows. 200 mg of the formulation was dosed intopoly(propylene) molds and the molds were closed. The molds were thenirradiated for 40 sec with an ultraviolet light source having anintensity of 1.82 mW/cm². The molds were then opened, and the moldhalves which had a lens attached were soaked in a mixture of 80%isopropanol, 20% water (v/v) overnight. The lenses were rinsed off themolds with this solvent mixture, then rinsed twice for 2 hrs. each infresh aliquots of isopropanol/water mixture. The lenses were drainedthen hydrated by immersion in deionized water. They were then rinsedthree times for 2 h apiece in pure water (3.0 mL/lens).

EXAMPLE 19

13.0 g of the formulation of Example 16 were weighed into an amber vial.0.853 g of alpha-omega dithio(polydimethylsiloxane) (MW 3,000 D,Shin-Etsu Co.) were added and the flask was stirred with a metal spatulafor 5 minutes, then rolled on a mill for 30 minutes. The formulation wastransferred to dosing syringes. The formulation was then used to castlenses as follows. 200 mg of the formulation was dosed intopoly(propylene) molds and the molds were closed. The molds were thenirradiated for 110 sec with an ultraviolet light source having anintensity of 1.82 mW/cm². The molds were then opened, and the lenseswere rinsed off the molds with hot water.

EXAMPLE 20

Attachment of Norbornene to PVA

100 grams of PVA (KL03) was dissolved in DMSO (477 grams) using a 1liter reaction kettle with stirring. 5-Norbornene-2-carboxaldehyde (5.67grams) was added to the solution. Concentrated HCl (37%) was added (29.3grams) to start the modification reaction. The solution was heated to40° C. and held for 18 hours. The solution was then cooled to roomtemperature. The polymer solution was added drop wise to a 10 to 15-foldexcess of a 20% aqueous NaCl solution with vigorous stirring. Thestirring was stopped and the PVA precipitate rose to the top of thevessel. The 20% NaCl was separated from the precipitate, then D.I. water(2.5 liters) was added to dissolve the modified PVA. The solution wasfiltered through a 0.45 μm filter cartridge, then ultrafiltered using 1KDa membranes. About an 8-fold volume of water passed through themembranes. The purified macromer solution was concentrated to >30%solids using a rotary evaporator.

EXAMPLE 21

Preparation of Formulation and Lens Fabrication

The 30.55% aqueous solution of the purified macromer (5.89 grams), 1%Irgacure 2959 solution in water (0.36 grams), hydroxyl-TEMPO (0.0064grams), and dithioerythritol (0.129 grams) were mixed together in asmall vial.

The curing characteristics were investigated by photo-rheology. Theformulations were cured using a 1.74 mW/cm² UV light source. The UV doseneeded for the shear modulus to level off at 28 kPa was 31 mJ/cm². Theresults from this test are attached at the end of this document.

EXAMPLE 22

Synthesis of Semi-Telechelic Silicone Hydrogel Polymer

A 2-L jacketed reactor was equipped with a heating/chilling loop, septuminlet adapter, reflux condenser with N2-inlet adapter, and overheadstirring. A solution was generated by dissolving 109.02 g of PDMS-DAmproduced by the procedure described in Example 12 and 12.37 g of thePDMS-DAm produced by Example 2 in 200 g of 1-propanol. This solution wascharged to the reactor and cooled to 8° C.

In a separate 500 mL flask equipped with magnetic stirring and avacuum-inlet adapter with valve, 5.63 g of cysteamine hydrochloride wasdissolved in 297 g of 1-propanol. In a 1-L flask equipped with magneticstirring and vacuum-inlet adapter with valve, 50.82 g ofN,N-dimethylacrylamide (Bimax Corporation), 16.55 g of hydroxyethylacrylate (Aldrich) and 5.08 g of aminopropyl methacrylamidehydrochloride (hereafter APMA, obtained from Polysciences Corp) weredissolved in 600 g of 1-propanol. In a 125 mL flask, similarly equipped,0.14 g of azo-bis(isobutyronitrile) (Aldrich) was dissolved in 14 g of1-propanol. And in a fourth, 100 mL flask, 1.70 g of hydroxyethylacrylate, 5.12 g of N,N-dimethylacrylamide, and 5.09 g of aminopropylmethacrylamide were dissolved in 60 g of dimethylsulfoxide. All foursolutions were degassed twice by evacuation to 60 mBar, holding vacuumfor 5 minutes, and then re-pressurizing with nitrogen.

Under a positive flow of nitrogen, the reactor was opened and thecysteamine hydrochloride and theN,N-dimethylacrylamide/hydroxyethylacrylate/aminopropyl methacrylamidehydrochloride solution in 1-propanol were charged to the reactor. Stillholding at 8° C., the reactor was degassed by evacuating to less than 5mBar and holding for 5 minutes, then re-pressurizing with nitrogen. Atotal of fifteen degassing cycles were performed. The dimethylsulfoxidesolution containing 0.72 g of hydroxyethyl acrylate, 2.88 g ofN,N-dimethylacrylamide and aminopropyl methacrylamide hydrochloride wascharged to the reservoir of an Alltech 301 HPLC pump equipped with anAlltech 590516 in-line degassing unit. The outlet was positioned toreturn fluid to the reservoir, and the pump was run at a rate of 0.353mL/min for 30 minutes to further deoxygenate the solution.

The reactor was then heated to 68° C., and the HPLC pump was stopped andits outlet affixed to drop fluid into the reaction mixture withoutcontacting the walls of the vessel. When at temperature, theazobis(isobutyronitrile) solution was injected into the reactor with asyringe and the HPLC pump was started. The solution was dosed to thereactor over three hours, and then 10 mL of filtered propanol was runthrough the HPLC lines into the reactor as a rinse. The reactor was thencooled to room temperature.

The reaction mixture was then transferred to a flask and vacuum strippedat 40° C./100 mBar on a rotary evaporator to remove 1-propanol. Afterthe first 344 g of 1-propanol was removed, 500 g of water were addedslowly with stirring to create an emulsion. The emulsion was thenfurther stripped of 1-propanol until 473 g of distillate were collected.600 g of water were again added back to the emulsion, andsolvent-exchange was continued to collect a final 150 g of distillate.The emulsion was then diluted to 4.0 kg.

EXAMPLE 23

Acrylamide-Functional Semi-Telechelic

2.0 kg of the emulsion produced in Example 22 was charged to a 2-Lreactor equipped with overhead stirring, refrigeration loop,thermometer, and the pH meter and dispensing tip of a Metrohm Model 718STAT Titrino. The reaction mixture was then cooled to 1° C. 1.5 g ofNaHCO₃ were charged to the emulsion and stirred to dissolve. The Titrinowas set to maintain pH at 9.5 by intermittent addition of 15% sodiumhydroxide solution. 6.2 mL of acryloyl chloride was then added over onehour using a syringe pump. The emulsion was stirred for another hour,then the Titrino was set to neutralize the reaction mixture by additionof a 15% solution of hydrochloric acid. The emulsion was then drainedfrom the reactor, diluted to 3.5 L and filtered to 16 μm exclusion. Theemulsion was purified by diafiltration (nominal molecular weightcut-off, 10,000 D) with deionized water until the permeate conductancewas below 2.5 μS/cm, and polymer was isolated by lyophilization. NuclearMagnetic Resonance spectroscopy revealed 0.15 mEq/g of carbon-carbondouble bonds.

EXAMPLE 24

Norbornyl-Functional Semi-Telechelic

The remaining 2.0 kg of emulsion from Example 22 was purified bydiafiltration (nominal molecular weight cut-off, 10,000 D) withdeionized water until the permeate conductance was less than 3.0 μS/cm².The material was then isolated by lyophilization.

18 g of the polymer thus produced was dissolved in approximately 200 mLof anhydrous, inhibitor-free tetrahydrofuran. 10 g of magnesium sulfatewere added and the flask was stirred for 30 minutes. The suspension wasfiltered to 1.2 μm exclusion with a glass-fiber filter paper and thentitrated to measure the amine equivalence. 207 g of solution with atotal equivalence of 2.78 mEq amine were recovered. 1.56 g ofdiazabicyclooctane (13.9 mEq) were added to the flask containing thesolution and stirred to dissolve. 2.18 g of the acid chloride of Example1 (13.9 mEq) were then diluted to 4 mL with anhydrous, inhibitor-freeTHF and added dropwise with a pipet. The flask was then equipped with areflux condenser with N2-inlet adapter and refluxed for three hours. Thereaction mixture was then diluted with 200 mL of deionized water. THFwas then removed from the solution on a rotary evaporator by stripping150-200 mL of fluid, back-adding water, and continuing to stripdistillate and back-add deionized water until an essentially aqueousemulsion remained. The emulsion was then diluted to 2.0 kg and broughtto alkaline pH by addition of 30 mL of 50% aqueous potassium hydroxide.This emulsion was stirred overnight, then ultrafiltered (nominalmolecular weight cut-off, 10,000 D) with deionized water until thepermeate conductance was below 70 μS/cm. The sample was then diafilteredwith 10% isopropanol in water, and finally ultrafiltered with a further60 L of water until no odor of norbornene carboxylic acid was detectedin the permeate. This norbornene-terminal polymer was isolated bylyophilization, and was analyzed and found to possess 0.159 mEq/g ofdouble bonds from norbornene.

EXAMPLE 25

Comparative Formulation: Free-Radical Curing

30.0 g of polymer from Example 23 was combined with 7.5 g of a 1%solution (80% 1-Propanol/20% tetrahydrofuran by weight) of2-hydroxy-4′-hydroxyethyl-2-methylpropiophenone (IRGACURE®-2959, CibaSpecialty Chemicals) and a further 8.64 g of solvent mixture in an amberglass vial and rolled until completely homogeneous.

EXAMPLE 26

Formulation of the Invention: 25% Hybrid Curing

4.93 g of formulation from Example 25 (0.481 mEq vinyl) were weighedinto a syringe. 0.1895 g of dithiol-terminated poly(dimethylsiloxane)with molecular weight 3000 (0.120 mEq thiol) were added and theformulation was stirred for five minutes with a steel spatula, thenrolled for one hour.

EXAMPLE 27

Formulation of the Invention: 50% Hybrid Curing

4.79 g of formulation from Example 25 (0.467 mEq vinyl) were weighedinto a vial. 0.368 g of dithiol-terminated poly(dimethylsiloxane) withmolecular weight 3000 (0.234 mEq thiol) were added and the formulationwas stirred for five minutes with a steel spatula, then rolled for onehour.

EXAMPLE 28

Formulation of the Invention: Full Thiol-Ene Curing

10.0 g of polymer from Example 23 was combined with 2.5 g of a 1%solution (80% 1-Propanol/20% tetrahydrofuran by weight) of2-hydroxy-4′-hydroxyethyl-2-methylpropiophenone (IRGACURE®-2959, CibaSpecialty Chemicals) and a further 2.88 g of solvent mixture in an amberglass vial and rolled until completely homogeneous. 3.098 g of thisformulation (0.32 mEq vinyl) were weighed into a new amber vial. 0.505 gof dithiol-terminated poly(dimethylsiloxane) with molecular weight 3000(0.32 mEq thiol) were added and the formulation was stirred for fiveminutes with a steel spatula, then rolled for one hour.

Lens Fabrication:

The formulations of Examples 25-28 were dosed into poly(propylene) moldsand the molds were closed. The molds were then irradiated for timesindicated in the table with an ultraviolet light source having anintensity of 4 mW/cm². The molds were then opened, and the mold halveswhich had a lens attached were rinsed with ethanol to remove the lenses.The lenses were then hydrated by immersion in deionized water,transferred to autoclave vials and immersed phosphate buffered salineand autoclaved. The moduli of the lenses were measured on an Instrontensile testing apparatus:

Example % Thiol-ene Exposure Modulus 25 0 16 sec N/A 26 25 13 sec 1.61MPa 27 50 20 sec 1.44 MPa 28 100 20 sec 0.79 MPa

As can be seen, increasing the amount of step-growth curing relative tofree-radical curing dramatically increases the softness of the lens, asseen by lower modulus.

1. A method for producing hydrogel contact lenses, comprising the stepsof: (1) obtaining a fluid composition, wherein the composition comprisesat least one first prepolymer having multiple first propagating groupsand a step-growth-propagating agent having two or more secondpropagating groups, wherein the first propagating groups areene-containing groups which are mono-valent or divalent radicals eachcontaining a carbon-carbon double bond which is not directly linked to acarbonyl group (—CO—), a benzene ring, a nitrogen atom, or an oxygenatom, wherein the second propagating groups are thiol groups eachco-reactive with one of the first propagating group in a photo-inducedstep-growth polymerization to form a hydrogel material; (2) introducingthe fluid composition into a cavity formed by a mold, wherein the moldhas a first mold half with a first molding surface defining the anteriorsurface of a contact lens and a second mold half with a second moldingsurface defining the posterior surface of the contact lens, wherein saidfirst and second mold halves are configured to receive each other suchthat a cavity is formed between said first and second molding surfaces;and (3) photo-inducing step-growth polymerization of the composition inthe mold to crosslink said at least one first prepolymer in the presenceof the step-growth propagating agent to form the hydrogel contact lens,wherein the first propagating groups are ene-containing groups offormula (II) or (III)

in which R₄-R₉, independent of each other, are hydrogen, C₁-C₁₀ alkenedivalent radical, C₁-C₁₀ alkyl, or —(R₁₈)_(a)—(X₁)_(b)—R₁₉ in which R₁₈is C₁-C₁₀ alkene divalent radical, X₁ is an ether linkage (—O—), aurethane linkage (—N), a urea linkage, an ester linkage, an amidlinkage, or carbonyl, R₁₉ is hydrogen, a single bond, amino group,carboxylic group, hydroxyl group, carbonyl group, C₁-C₁₂ aminoalkylgroup, C₁-C₁₈ alkylaminoalkyl group, C₁-C₁₈ carboxyalkyl group, C₁-C₁₈hydroxyalkyl group, C₁-C₁₈ alkylalkoxy group, C₁-C₁₂ aminoalkoxy group,C₁-C₁₈ alkylaminoalkoxy group, C₁-C₁₈ carboxyalkoxy group, or C₁-C₁₈hydroxyalkoxy group, a and b independent of each other is zero or 1,optionally R₄-R₉ are linked through an alkene divalent radical to form acyclic ring, provided that at least one of R₄-R₉ are divalent radicals;n and m independent of each other are integer number from 0 to 9,provided that the sum of n and m is an integer number from 2 to 9;R₁₀-R₁₇, independent of each other, are hydrogen, C₁-C₁₀ alkene divalentradical, C₁-C₁₀ alkyl, or —(R₁₈)_(a)—(X₁)_(b)—R₁₉, p is an integernumber from 1 to 3, provided that only one or two of R₁₀-R₁₇ aredivalent radicals.
 2. The method of claim 1, wherein said at least onefirst prepolymer is obtained from a copolymer with pendant or terminalfunctional groups by covalently attaching the ene-containing groups tothe pendant or terminal functional groups of the copolymer, wherein thefirst prepolymer is capable of forming a hydrogel material.
 3. Themethod of claim 2, wherein the copolymer with the pendant or terminalfunctional groups comprises siloxane units.
 4. The method of claim 2,wherein the copolymer with the pendant or terminal functional groups isselected from the group consisting of: (1) a copolymer of vinyl alcoholwith one or more vinylic monomers in the presence or absence of acrosslinking agent; (2) a copolymer of C₃-C₈ aminoalkylacrylate with oneor more vinylic monomers in the presence or absence of a crosslinkingagent; (3) a copolymer of C₃-C₈ hydroxyalkylacrylate with one or morevinylic monomers in the presence or absence of a crosslinking agent; (4)a copolymer of C₄-C₈ aminoalkylmethacrylate with one or more vinylicmonomers in the presence or absence of a crosslinking agent; (5) acopolymer of C₄-C₈ hydroxyalkylmethacrylate with one or more vinylicmonomers in the presence or absence of a crosslinking agent; (6) acopolymer of C₃-C₈ alkylacrylic acid with one or more vinylic monomersin the presence or absence of a crosslinking agent; (7) a copolymer ofC₄-C₈ alkylmethacrylic with one or more vinylic monomers in the presenceor absence of a crosslinking agent; (8) a copolymer of anepoxy-containing acrylate monomer with one or more vinylic monomers inthe presence or absence of a crosslinking agent; (9) a copolymer of anepoxy-containing methacrylate monomer with one or more vinylic monomersin the presence or absence of a crosslinking agent; (10) an amine- orisocyanate-capped polyurea obtained by copolymerization of a mixturecomprising (a) at least one poly(oxyalkylene)diamine, (b) optionally atleast one organic di- or poly-amine, (c) optionally at least onediisocyanate, and (d) at least one polyisocyanate; (11) a hydroxy- orisocyanate-capped polyurethane obtained by copolymerization of a mixturecomprising (a) at least one poly(oxyalkylene)diol, (b) optionally atleast one organic compound with di- or poly-hydroxy group, (c)optionally at least one diisocyanate, and (d) at least onepolyisocyanate; (12) a siloxane-containing copolymer obtained bycopolymerizing a mixture containing at least one polymerizable componentselected from the consisting of a siloxane-containing vinylic monomer, asiloxane-containing macromer with acryloyl groups, a siloxane-containingmacromer with methacryloyl groups, a silicone-containing prepolymer withacryloyl, a silicone-containing prepolymer with methacryloyl groups, andcombinations thereof; and (13) a copolymer of a poly(di-C₁₋₁₂alkylsiloxane) with one or more coreactive monomers.
 5. The method ofclaim 2, wherein said the first propagating groups are ene-containinggroups of formula (III).
 6. The method of claim 2, wherein said thefirst propagating groups are ene-containing groups of formula (II). 7.The method of claim 2, wherein the fluid composition comprises a thirdprepolymer having multiple acryloyl

or methacryloyl

groups.
 8. The method of claim 2, wherein the fluid composition issubstantially free of vinylic monomer and crosslinking agent.
 9. Themethod of claim 1, wherein said at least one first prepolymer isobtained by copolymerization of a polymerizable mixture comprising atleast one monomer having one ene-group of formula (II) or (III) and oneethylenically unsaturated group.
 10. The method of claim 1, wherein themold is a reusable mold.
 11. The method of claim 10, wherein the step(3) is performed by means of a spatial limitation of actinic radiationto crosslink the first prepolymer.
 12. The method of claim 4, whereinsaid the first propagating groups are ene-containing groups of formula(III).
 13. The method of claim 4, wherein said the first propagatinggroups are ene-containing groups of formula (II).
 14. The method ofclaim 4, wherein the fluid composition comprises a third prepolymerhaving multiple acryloyl

or methacryloyl

groups.
 15. The method of claim 4, wherein the fluid composition issubstantially free of vinylic monomer and crosslinking agent.
 16. Themethod of claim 3, wherein said the first propagating groups areene-containing groups of formula (III).
 17. The method of claim 4,wherein the mold is a reusable mold.
 18. A method for producing hydrogelcontact lenses, comprising the steps of: (1) obtaining a fluidcomposition, wherein the composition comprises at least one firstprepolymer having multiple first propagating groups and astep-growth-propagating agent having two or more second propagatinggroups, wherein the first propagating groups are ene-containing groupswhich are mono-valent or divalent radicals each containing acarbon-carbon double bond which is not direactly linked to a carbonylgroup (—CO—), a benzene ring, a nitrogen atom, or an oxygen atom,wherein the second propagating groups are thiol groups each co-reactivewith one of the first propagating group in a photo-induced step-growthpolymerization to form a hydrogel material; (2) introducing the fluidcomposition into a cavity formed by a mold, wherein the mold has a firstmold half with a first molding surface defining the anterior surface ofa contact lens and a second mold half with a second molding surfacedefining the posterior surface of the contact lens, wherein said firstand second mold halves are configured to receive each other such that acavity is formed between said first and second molding surfaces; and (3)photo-inducing step-growth polymerization of the composition in the moldto crosslink said at least one first prepolymer in the presence of thestep-growth propagating agent to form the hydrogel contact lens, whereinsaid the first propagating groups are ene-containing groups of formula(I), (II), or (III)

in which R₁ is hydrogen, or C₁-C₁₀ alkyl; R₂ and R₃ independent of eachother are hydrogen, C₁-C₁₀ alkene divalent radical, C₁-C₁₀ alkyl, or—(R₁₈)_(a)—(X₁)_(b)—R₁₉ in which R₁₈ is C₁-C₁₀ alkene divalent radical,X₁ is an ether linkage (—O—), a urethane linkage (—N), a urea linkage,an ester linkage, an amid linkage, or carbonyl, R₁₉ is hydrogen, asingle bond, amino group, carboxylic group, hydroxyl group, carbonylgroup, C₁-C₁₂ aminoalkyl group, C₁-C₁₈ alkylaminoalkyl group, C₁-C₁₈carboxyalkyl group, C₁-C₁₈ hydroxyalkyl group, C₁-C₁₈ alkylalkoxy group,C₁-C₁₂ aminoalkoxy group, C₁-C₁₈ alkylaminoalkoxy group, C₁-C₁₈carboxyalkoxy group, or C₁-C₁₈ hydroxyalkoxy group, a and b independentof each other is zero or 1, provided that only one of R₂ and R₃ is adivalent radical; R₄-R₉, independent of each other, are hydrogen, C₁-C₁₀alkene divalent radical, C₁-C₁₀ alkyl, or —(R₁₈)_(a)—(X₁)_(b)—R₁₉,optionally R₄ and R₉ are linked through an alkene divalent radical toform a cyclic ring, provided that at least one of R₄-R₉ are divalentradicals; n and m independent of each other are integer number from 0 to9, provided that the sum of n and m is an integer number from 2 to 9;R₁₀-R₁₇, independent of each other, are hydrogen, C₁-C₁₀ alkene divalentradical, C₁-C₁₀ alkyl, or —(R₁₈)_(a)—(X₁)_(b)—R₁₉, p is an integernumber from 1 to 3, provided that only one or two of R₁₀-R₁₇ aredivalent radicals, wherein said at least one first prepolymer isobtained from a copolymer with pendant or terminal functional groups bycovalently attaching the ene-containing groups to the pendant orterminal functional groups of the copolymer, wherein the firstprepolymer is capable of forming a hydrogel material, and wherein thecopolymer with the pendant or terminal functional groups comprisessiloxane units.